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appendix L

java.util Package Reference

CONTENTS

The java.util package contains a variety of classes representing data structures and other miscellaneous features such as support for date and time.

Enumeration

The Enumeration interface defines methods that can be used to iterate through a set of objects.

hasMoreElements

public abstract boolean hasMoreElements()
Can be used to determine if the enumeration has more elements.
Returns: true if there are more elements, false if not.

nextElement

public abstract Object nextElement()
This method returns the next element in the enumeration. Calling it repeatedly will move through the enumeration.
Returns: The next element in the enumeration.
Throws: NoSuchElementException if there are no more elements in the enumeration.

Observer

The Observer interface defines an update method that is invoked by an Observable object whenever the Observable object has changed and wants to notify its observers.

update

public abstract void update(Observable o, Object arg)
This method is called whenever an Observable instance that is being observed invokes either of its notifyObservers methods.
Parameters:
o-the Observable object that is generating this message.
arg-any additional information passed by the Observable object's notifyObservers method.

BitSet

Extends: Object
Implements: Cloneable
This class represents a dynamically sized set of bits. Two constructors are provided, one that creates an empty set of unspecified size and one that creates a set of a specified size. The set method can be used to set an individual bit, or clear can be used to clear an individual bit.

BitSet Constructor

public BitSet()
This constructor creates an empty bit set.

BitSet Constructor

public BitSet(int nbits)
This constructor creates an empty bit set with the specified number of bits.
Parameters: nbits-the number of bits in the set.

and

public void and(BitSet set)
This method logically ANDs the bit set with another bit set.
Parameters: set-the bit set to AND with the current set.

clear

public void clear(int bit)
Clears the specified bit.
Parameters: bit-the bit to clear.

clone

public Object clone()
This method overrides the clone method in Object. It can be used to clone the bit set.

equals

public boolean equals(Object obj)
This method can be used to compare the contents of two bit sets. If the same bits are set in the two bit sets, they are considered equal.
Parameters: obj-the bit set to compare against.
Returns: true if the set bits are the same, false otherwise.

get

public boolean get(int bit)
Gets the value of a specified bit in the set.
Parameters: bit-the bit to get.
Returns: true if the bit is set; false if it is clear.

hashCode

public int hashCode()
This method overrides the hashCode method in Object and can be used to get a hash code for the instance.
Returns: A hash code for the instance.

or

public void or(BitSet set)
This method logically ORs the bit set with another.
Parameters: set-the bit set to OR with the current set.

set

public void set(int bit)
Sets the specified bit.
Parameters: bit-the bit to set.

size

public int size()
This method returns the amount of space, in bits, used to store the set. Space for a bit set is allocated in 64-bit increments.
Returns: The amount of space, in bits, used to store the bit set.

toString

public String toString()
This method formats the bit set as a string. The string will consist of an opening curly brace, comma-separated values representing each set bit, and a closing curly brace.
Returns: A string representing the bits in the bit set that are set.

xor

public void xor(BitSet set)
This method logically XORs the bit set with another bit set.
Parameters: set-the bit set to XOR with the current set.

Date

Extends: Object
The Date class stores a representation of a date and time and provides methods for manipulating the date and time components. Constructors are provided that will create a new Date instance based on the current date and time, the UNIX-standard milliseconds since midnight on January 1, 1970, a string, or from integers representing the year, month, day, hours, minutes, and seconds.

Date Constructor

public Date()
This method creates a new Date object using today's date.

Date Constructor

public Date(long date)
This method creates a date from a long that represents the number of milliseconds since January 1, 1970.
Parameters: date-the number of milliseconds since January 1, 1970.

Date Constructor

public Date(int year, int month, int date)
This method creates a new Date object that corresponds to the year, month, and day passed to it. The first month of the year is month zero. The day of the month is normalized so that impossible dates become real dates.
Parameters:
year-the number of years since 1900.
month-the zero-based month, from 0 to 11.
date-the day of the month.

Date Constructor

public Date(int year, int month, int date, int hrs, int min)
This method creates a new Date object that corresponds to the year, month, day, hours, and minutes passed to it. As with the prior constructor, the day of the month is normalized so that impossible dates become real dates.
Parameters:
year-the number of years since 1900.
month-the zero-based month, from 0 to 11.
date-the day of the month.
hrs-the zero-based number of hours (0-23).
min-the zero-based number of minutes (0-59).

Date Constructor

public Date(int year, int month, int date, int hrs, int min,
int sec)
This method creates a new Date object that corresponds to the year, month, day, hour, minute, and seconds passed to it. As with the other constructors, the day of the month is normalized so that impossible dates become real dates.
Parameters:
year-the number of years since 1900.
month-the zero-based month, from 0 to 11.
date-the day of the month.
hrs-the zero-based number of hours (0-23).
min-the zero-based number of minutes (0-59).
sec-the zero-based number of seconds (0-59).

Date Constructor

public Date(String s)
This method creates a new date based on the date string passed to it.
Parameters: s-a time string in the format passed to java.util.Date.Parse, as described later in this appendix.

UTC

public static long UTC(int year, int month, int date, int
hrs, int min, int sec)
This method calculates the time in UTC (Coordinated Universal Time) format based on the specified parameters. Parameters are expected to be given in UTC values, not the time in the local time zone.
Parameters:
year-the number of years since 1900.
month-the zero-based month, from 0 to 11.
date-the day of the month.
hrs-the zero-based number of hours (0-23).
min-the zero-based number of minutes (0-59).
sec-the zero-based number of seconds (0-59).
Returns: A UTC time value.

parse

public static long parse(String s)
This method calculates the time in UTC format based on the string passed to it.
Parameters: s-a formatted time string such as Mon, 8 Apr 1996 21:32:PM PST.
Returns: A UTC time value.

after

public boolean after(Date when)
Determines whether the Date occurs after the specified date.
Parameters: when-the date to compare against.
Returns: true if the object's date occurs after the specified date; false otherwise.

before

public boolean before(Date when)
This method determines whether the Date occurs before the specified date.
Parameters: when-the date to compare against.
Returns: true if the object's date occurs before the specified date; false otherwise.

equals

public boolean equals(Object obj)
This method determines whether two Date objects are the same by comparing the dates represented by each object.
Parameters: obj-the object to compare against.
Returns: true if the dates are the same; false otherwise.

getDate

public int getDate()
This method returns the day (or date) portion of a Date object.
Returns: The day of the month, from 1 to 31.

getDay

public int getDay()
This method returns the day of the week. Sunday is assigned a value of 0.
Returns: The day of the week from 0 (Sunday) to 6 (Saturday).

getHours

public int getHours()
This method returns the hour.
Returns: The hour from 0 to 23.

getMinutes

public int getMinutes()
This method returns the minutes.
Returns: The minutes from 0 to 59.

getMonth

public int getMonth()
This method returns the month.
Returns: The month from 0 (January) to 11 (December).

getSeconds

public int getSeconds()
This method returns the seconds.
Returns: The seconds from 0 to 59.

getTime

public long getTime()
This method returns the number of milliseconds since midnight on January 1, 1970.
Returns: The time expressed in elapsed milliseconds.

getTimezoneOffset

public int get`TimezoneOffset()
This method returns the offset in minutes of the current time zone from the UTC.
Returns: The number of minutes difference between the time zone of the object and UTC.

getYear

public int getYear()
This method returns the year after 1900.
Returns: The year after 1900.

hashCode

public int hashCode()
This method overrides the hashCode method in Object and can be used to get a hash code for the instance.
Returns: A hash code for the instance.

setDate

public void setDate(int date)
This method sets the day of the month portion of a Date object.
Parameters: date-the day value.

setHours

public void setHours(int hours)
This method sets the hours portion of a Date object.
Parameters: hours-the hour from 0 (midnight) to 23.

setMinutes

public void setMinutes(int minutes)
This method sets the minutes portion of a Date object.
Parameters: minutes-the minutes from 0 to 59.

setMonth

public void setMonth(int month)
This method sets the month portion of a Date object.
Parameters: month-the zero-based month from 0 (January) to 11 (December).

setSeconds

public void setSeconds(int seconds)
This method sets the seconds portion of a Date object.
Parameters: seconds-the seconds from 0 to 59.

setTime

public void setTime(long time)
This method sets the time to the time represented by the number of milliseconds in the time parameter. It is frequently used in conjunction with the getTime method that returns a number of milliseconds.
Parameters: time-the new time in milliseconds since January 1, 1970.

setYear

public void setYear(int year)
This method sets the year portion of a Date instance.
Parameters: year-the year after 1900 (for 1996, use 96).

toGMTString

public String toGMTString()
This method creates a string that contains the date and time formatted according to GMT (Greenwich Mean Time) conventions.
Returns: A string representing the date in GMT format, such as 14 Nov 1995 08:00:00 GMT.

toLocaleString

public String toLocaleString()
This method creates a string that contains the date and time in the format of the current locale.
Returns: A string representing the date as formatted for the locale of the instance, such as
11/14/95 00:00:00.

toString

public String toString()
This method creates a string that contains the day of the week, the date, and the time.
Returns: A string representing the day of the week, date and time of the instance, such as
Tue Nov 14 00:00:00 1995.

Dictionary

Extends: Object
The Dictionary class is an abstract class. Each element in a Dictionary consists of a key and value. Elements are added to a Dictionary using put and are retrieved using get. Elements may be deleted with remove. The methods elements and keys each return an enumeration of the values and keys, respectively, stored in the Dictionary.

Dictionary Constructor

public Dictionary()
This is a default constructor that will create an empty dictionary.

elements

public abstract Enumeration elements()
This abstract method returns an enumeration of all elements in a dictionary.
Returns: An enumeration of each of the elements in the dictionary. The methods of Enumeration can be used to iterate through the elements.

get

public abstract Object get(Object key)
This abstract method retrieves an object from a dictionary based on its key.
Parameters: key-the key of the object to be retrieved.
Returns: The value associated with the key, if found; null if not.

isEmpty

public abstract boolean isEmpty()
This abstract method can be used to determine if the dictionary is empty.
Returns: true if the dictionary is empty; false if not.

keys

public abstract Enumeration keys()
This abstract method returns an enumeration of all keys in a dictionary.
Returns: An enumeration of each of the keys in the dictionary. The methods of Enumeration can be used to iterate through the keys.

put

public abstract Object put(Object key, Object value)
This abstract method inserts a new element into the dictionary. To retrieve an element, use the get method.
Parameters:
key-the key to be added.
value-the value associated with the key.
Returns: If the key was already in the dictionary, the old value associated with it is returned. If not, null is returned.
Throws: NullPointerException if the value is null.

remove

public abstract Object remove(Object key)
This abstract method removes an object from a dictionary.
Parameters: key-the key of the element to be removed.
Returns: If the key is found, the value associated with it is returned; if not, null is returned.

size

public abstract int size()
This abstract method returns the number of elements in the dictionary.
Returns: The number of items stored in the dictionary.

Hashtable

Extends: Dictionary
The Hashtable class is used for mapping keys to values. Each element in a hash table consists of a key and a value. Elements are added to a hash table using the put method and are retrieved using get. Elements may be deleted from a hash table with remove. A hash table will expand in size as elements are added to it. When creating a new hash table, you can specify an initial capacity and a load factor. The hash table will increase in size whenever adding a new element would move the hash table past its threshold. A hash table's threshold is its capacity multiplied by its load factor. For example, a hash table with a capacity of 100 and a load factor of 0.75 would have a threshold of 75 items.

Hashtable Constructor

public Hashtable(int initialCapacity, float loadFactor)
This constructor creates a new instance of a hash table with the specified initial capacity and load factor. Although an initial capacity is specified, the hash table will grow as needed when new items are added. The initial capacity specifies how many elements could be stored in the hash table if the load factor is 1.0. The load factor is a number between 0.0 and 1.0 and specifies the percentage of the hash table that must be full before the size is automatically increased.
Parameters:
initialCapacity-the initial capacity of the hash table.
loadFactor-a value between 0.0 and 1.0 that specifies the percent of available hash slots that can be filled before the table is automatically rehashed into a large hash table.

Hashtable Constructor

public Hashtable(int initialCapacity)
This constructor creates a new hash table with the specified initial capacity and a default load factor of 0.75.
Parameters: initialCapacity-the initial capacity of the hash table.

Hashtable Constructor

public Hashtable()
This constructor creates a new hash table using default values for the initial capacity and the load factor. A default of 101 is used for the initial capacity, and 0.75 is used for the load factor.

clear

public synchronized void clear()
This method will remove all elements from a hash table.

clone

public synchronized Object clone()
This method clones the hash table into a new hash table. The keys and values themselves are not cloned.
Returns: A cloned hash table.

contains

public synchronized boolean contains(Object value)
This method searches the hash table to determine if a specific value is stored.
Parameters: value-the value to search for.
Returns: true if the value is found; false if not.
Throws: NullPointerException if the value is null.

containsKey

public synchronized boolean containsKey(Object key)
This method searches the hash table to determine if a specific key occurs.
Parameters: key-the key to search for.
Returns: true if the key is found; false if not.

elements

public synchronized Enumeration elements()
This method returns an enumeration of all of the element values in the instance.
Returns: An enumeration of each of the keys in the hash table. The methods of Enumeration can be used to iterate through the keys.

get

public synchronized Object get(Object key)
This method retrieves the object associated with the specified key.
Parameters: key-the key of the object to be retrieved.
Returns: The value associated with the key, if found; null if not.

isEmpty

public boolean isEmpty()
This method can be used to determine if the hash table is empty.
Returns: true if the hash table is empty; false if not.

keys

public synchronized Enumeration keys()
This method returns an enumeration of all the keys in the instance.
Returns: An enumeration of each of the keys in the hash table. The methods of Enumeration can be used to iterate through the keys.

put

public synchronized Object put(Object key, Object value)
This method inserts a new element into the hash table. To retrieve an element, use the get method.
Parameters:
key-the key to be added.
value-the value associated with the key.
Returns: If the key was already in the hash table, the old value associated with it is returned. If not, null is returned.
Throws: NullPointerException if the value is null.

rehash

protected void rehash()
This method rehashes the hash table into a larger hash table. It is not normally necessary to call this method directly because it is invoked automatically based on the capacity and load factor of the hash table.

remove

public synchronized Object remove(Object key)
This method removes an object from a hash table.
Parameters: key-the key of the element to be removed.
Returns: If the key is found, the value associated with it is returned; if not, null is returned.

size

public int size()
This method returns the number of elements in the hash table.
Returns: The number of items stored in the hash table.

toString

public synchronized String toString()
This method overrides the toString method in Object and formats the contents of the hash table as a string.
Returns: A string representation of the hash table.

Observable

Extends: Object
An Observable class is a class that can be watched or monitored by another class that implements the Observer interface. Associated with an Observable instance is a list of observers. Whenever the Observable instance changes it can notify each of its observers. By using Observable and Observer classes you can achieve a better partitioning of your code by decreasing the reliance of one class on another.

Observable Constructor

public Observable()
This is an empty, default constructor.

addObserver

public synchronized void addObserver(Observer o)
This method will add an observer to the list of objects that are observing this instance. The observer must implement the Observer interface.
Parameters: o-the observer to add.

clearChanged

protected synchronized void clearChanged()
This method clears the internal flag that indicates an Observable instance has changed.

countObservers

public synchronized int countObservers()
This method counts the numbers of observers who are observing the instance.
Returns: The number of observers for the instance.

deleteObserver

public synchronized void deleteObserver(Observer o)
This method will delete an observer from the list of observers that are monitoring an Observable object. The observer must have been previously added with addObserver.
Parameters: o-the observer to delete.

deleteObservers

public synchronized void deleteObservers()
This method will delete all observers of the Observable instance.

hasChanged

public synchronized boolean hasChanged()
This method can be used to query if an Observable has changed.
Returns: true if an observable change has occurred; false otherwise.

notifyObservers

public void notifyObservers()
This method will notify all observers that a change has occurred in the Observable object. This will result in a call to the update method in each observer.

notifyObservers

public synchronized void notifyObservers(Object arg)
This method will notify all observers that a change has occurred in the Observable object. This will result in a call to the update method in each observer to which arg will be passed.
Parameters: arg-any object that can be used to convey information to the observers.

setChanged

protected synchronized void setChanged()
This method sets an internal flag to indicate that an observable change has occurred within the instance.

Properties

Extends: Hashtable
The Properties class can be used to store keys and associated values. Through its save and load methods, Properties can be written to disk. This makes this class an excellent mechanism for storing configuration information between runs of a program.

Member Variables

protected Properties defaults
This member stores the default property values.

Properties Constructor

public Properties()
This constructor is used to create an empty, new instance of Properties.

Properties Constructor

public Properties(Properties defaults)
This constructor will create a new instance of Properties and will establish a set of default properties.

getProperty

public String getProperty(String key)
This method is used to retrieve a property based on its key. If no matching key is found, the defaults are searched. If no match is found there either, null is returned.
Parameters: key-the key of the property to retrieve.
Returns: The property associated with the key or null if there is no matching key.

getProperty

public String getProperty(String key, String defaultValue)
This method is used to retrieve a property based on its key. If no match is found, defaultValue is returned.
Parameters:
key-the key of the property to retrieve.
defaultValue-the value to use if no matching key is found.
Returns: The property associated with the key or the defaultValue if there is no matching key.

list

public void list(PrintStream out)
This method will list all of the properties to the specified PrintStream. It is useful mainly while debugging.
Parameters: out-the PrintStream where the properties are to be printed.

load

public synchronized void load(InputStream in) throws IOException
This method reads a set of properties from the specified InputStream. Used in conjunction with the save method, Properties can be written to disk at the end of a program run and then reloaded at the start of the next run.
Parameters: in-the input stream from which the properties are to be read.
Throws: IOException if the specified file is not found or cannot be read.

propertyNames

public Enumeration propertyNames()
This method returns an enumeration of all of the property names in the instance.
Returns: An enumeration of each of the property names. The methods of Enumeration can be used to iterate through the property names.

save

public synchronized void save(OutputStream out, String header)
This method saves the properties to an output stream. Since FileOutputStream is a subclass of OutputStream, this method can be used to write to a file.
Parameters:
out-the output stream to which the properties are to be written.
header-a header that will be sent to the output stream before the properties.

Random

Extends: Object
The Random class represents a pseudo-random number generator. Two constructors are provided, one taking a seed value as a parameter and the other taking no parameters and using the current time as a seed.

random Constructor

public random()
This constructor creates a new random number generator that is seeded based on the current time.

random Constructor

public random(long seed)
This constructor creates a new random number generator based on the specified seed value. A program can reset the seed of an already created instance by using the setSeed method.
Parameters: seed-the seed value.

nextDouble

public double nextDouble()
This method retrieves the next number from the random number generator. The number will be a pseudo-random, uniformly distributed double between 0.0D and 1.0D.
Returns: A randomly distributed double between 0.0D and 1.0D.

nextFloat

public float nextFloat()
This method retrieves the next number from the random number generator. The number will be a pseudo-random, uniformly distributed float between 0.0F and 1.0F.
Returns: A randomly distributed float between 0.0F and 1.0F.

nextGaussian

public synchronized double nextGaussian()
This method retrieves the next value from the pseudo-random number generator. The value will be returned as a Gaussian-distributed double that has a mean of 0 and a standard deviation of 1.
Returns: A Gaussian-distributed double.

nextInt

public int nextInt()
This method retrieves the next number from the random number generator. The number will be a pseudo-random int with a value that is uniformly distributed among all possible int values.
Returns: A randomly distributed int.

nextLong

public long nextLong()
This method retrieves the next number from the random number generator. The number will be a pseudo-random long with a value that is uniformly distributed among all possible long values.
Returns: A randomly distributed long.

setSeed

public synchronized void setSeed(long seed)
This method sets a seed value for the pseudo-random number generator. The seed value is used to determine the values that are generated. By setting a specific seed value, the random number generator can be coerced into generating a specific sequence of values.
Parameters: seed-the seed value.

Stack

Extends: Vector
The Stack class implements a simple last-in-first-out stack. An item is stored on a stack by "pushing" it onto the stack. An item may subsequently be "popped" off the stack and used. The item popped off a stack will always be the most recently pushed item.

Stack Constructor

public Stack()
This is the default constructor.

empty

public boolean empty()
This method can be used to determine if the stack contains items.
Returns: true if the stack is empty; false otherwise.

peek

public Object peek()
This method can be used to peek at the top item on the stack. It is similar to pop but does not remove the item from the stack.
Returns: The item at the top of the stack.
Throws: EmptyStackException if the stack is empty.

pop

public Object pop()
This method retrieves the last item added to the stack. To examine, but not remove, the top item in the stack use the peek method.
Returns: The item at the top of the stack.
Throws: EmptyStackException if the stack is empty.

push

public Object push(Object item)
This method adds a new item to the stack.
Parameters: item-the item to push onto the stack.
Returns: The item that was pushed onto the stack.

search

public int search(Object o)
This method examines the stack to see if the specified object is in the stack.
Parameters: o-the object to search for.
Returns: The distance from the top of the stack, or -1 if the item is not in the stack.

StringTokenizer

Extends: Object
Implements: Enumeration
A StringTokenizer can be used to parse a string into its constituent tokens. For example, each word in a sentence could be considered a token. However, the StringTokenizer class goes beyond the parsing of sentences. You can create a fully customized tokenizer by specifying the set of token delimiters when the string tokenizer is created.

StringTokenizer Constructor

public StringTokenizer(String str, String delim, boolean returnTokens)
This constructor creates a new instance based on the string to be tokenized, the set of delimiters, and a flag indicating if delimiters should be returned as tokens.
Parameters:
str-the string to be tokenized.
delim-a string containing the delimiters to use when tokenizing the string.
returnTokens-true if the string tokenizer should return delimiters as tokens; false if not.

StringTokenizer Constructor

public StringTokenizer(String str, String delim)
This constructor creates a new instance based on the string to be tokenized and a set of delimiters.
Parameters:
str-the string to be tokenized.
delim-a string containing the delimiters to use when tokenizing the string.

StringTokenizer Constructor

public StringTokenizer(String str)
This constructor creates a new instance based on the string to be tokenized and the default set of delimiters. The default delimiters are the space, tab, newline, and carriage-return characters.

countTokens

public int countTokens()
This method returns the number of remaining tokens.
Returns: The quantity of tokens remaining in the string being tokenized.

hasMoreElements

public boolean hasMoreElements()
This method can be used to determine if the string tokenizer contains more elements (tokens). This method is identical to hasMoreTokens and is a member of StringTokenizer because StringTokenizer implements the Enumeration interface.
Returns: true if there are more elements; false otherwise.

hasMoreTokens

public boolean hasMoreTokens()
This method can be used to determine if the string tokenizer contains more tokens. It is identical to hasMoreElements.
Returns: true if there are more tokens; false otherwise.

nextElement

public Object nextElement()
This method overrides nextElement in the Enumeration interface and exists because StringTokenizer implements that interface. It is identical to nextToken and returns the next token in the enumeration.
Returns: The next token in the enumeration.
Throws: NoSuchElementException if there are no more elements.

nextToken

public String nextToken()
This method returns the next token in the string that is being tokenized. It is typically used inside a loop that processes each token.
Returns: The next token in the string being tokenized.
Throws: NoSuchElementException if there are no more tokens.

nextToken

public String nextToken(String delim)
This method changes the set of delimiter characters and then returns the next token. The new delimiter set will remain in effect after this method completes.
Parameters: delim-a string containing the new set of delimiters.
Returns: The next token in the string being tokenized.
Throws: NoSuchElementException if there are no more tokens.

Vector

Extends: Object
Implements: Cloneable
A vector is analogous to a linked list in other languages or class libraries. A vector stores items of type Object so it can be used to store instances of any Java class. A single vector may store different elements that are instances of different classes.

Vector Constructor

public Vector(int initialCapacity, int capacityIncrement)
This constructor will create a new instance of a vector with space for initialCapacity elements initially. Memory for additional elements will be allocated in blocks that will each hold capacityIncrement elements.
Parameters:
initialCapacity-the number of elements to allocate space for when the object is created.
capacityIncrement-the number of additional elements to allocate space for whenever additional space is needed.

Vector Constructor

public Vector(int initialCapacity)
This constructor will create a new instance of a vector with space for initialCapacity elements initially. Whenever a new element is added that would have exceeded this capacity, the size of the vector is doubled.
Parameters: initialCapacity-the number of elements to allocate space for when the object is created.

Vector Constructor

public constructorVector()
This constructor will create a new instance of a vector. Initially, the vector will have room for storing 10 elements, but this will increase automatically to accommodate new elements. Whenever a new element is added that would have exceeded this capacity, the size of the vector is doubled.

Member Variables

protected int capacityIncrement
This member stores the amount by which the vector will be incremented each time it needs to grow. If capacityIncrement is 0, the buffer does not grow by a fixed amount but instead doubles whenever it needs to grow.
protected int elementCount
This member stores the number of elements in the vector.
protected Object elementData[]
This member is the array where the Vector elements are stored.

addElement

public final synchronized void addElement(Object obj)
This method is used to insert new elements into the vector; a vector can store objects of different types.
Parameters: obj-the object to add to the vector.

capacity

public final int capacity()
This method returns the number of elements that will fit in the vector before more space is allocated.
Returns: The number of elements that will fit in the currently allocated portion of the vector.

clone

public synchronized Object clone()
This method overrides clone in Object and will clone the vector. Only the vector itself is cloned; the elements of the vector are not cloned.
Returns: A cloned copy of the vector.

contains

public final boolean contains(Object elem)
This method determines if an object is stored in a vector.
Returns: true if the object is stored in the vector; false otherwise.

copyInto

public final synchronized void copyInto(Object anArray[])
This method copies the elements of the vector into an array.
Parameters: anArray-the array into which the vector elements will be copied.

elementAt

public final synchronized Object elementAt(int index)
This method retrieves the element located at the specified index within the vector.
Parameters: index-the zero-based index number of the element to retrieve.
Returns: The element at the specified zero-based index.
Throws: ArrayIndexOutOfBoundsException if an invalid index is specified.

elements

public final synchronized Enumeration elements()
This method returns an Enumeration of the elements in the vector, making it easy to iterate through the elements.
Returns: An Enumeration consisting of all the elements in the vector.

ensureCapacity

public final synchronized void ensureCapacity(int minCapacity)
This method ensures that the vector has at least the specified minimum capacity. If the current capacity of the vector is less than minCapacity, the size of the vector is increased to hold at least minCapacity.
Parameters: minCapacity-the minimum capacity of the vector.

firstElement

public final synchronized Object firstElement()
This method retrieves the first element in the vector. If the vector is empty, an exception is thrown. It performs the same function as elementAt(0).
Returns: The element at the specified zero-based index.
Throws: NoSuchElementException if the vector is empty.

indexOf

public final int indexOf(Object elem)
This method searches the vector and returns the zero-based index number of the first matching object.
Parameters: elem-the element to find the index of.
Returns: The element number of the first element that matches elem, or -1 if no match is found.

indexOf

public final synchronized int indexOf(Object elem, int index)
This method finds the first element in the vector that matches elem starting at the element given by index. It is very useful for traversing a vector searching for all elements matching a specific object.
Parameters:
elem-the element to find the index of.
index-the index number at which to start the search.
Returns: The element number of the first element that matches elem, or -1 if no match is found.

insertElementAt

public final synchronized void insertElementAt(Object obj,
int index)
This method, like addElement, is used to add a new element to a vector. However, this method can be used to specify where in the vector the new element should be added. All Vector elements with index numbers greater than or equal to index are moved to make room for the new element.
Parameters:
obj-the object to add to the vector.
index-the zero-based index at which the object is to be inserted.
Throws: ArrayIndexOutOfBoundsException if the specified index is invalid.

isEmpty

public final boolean isEmpty()
This method is used to determine if the vector contains any elements.
Returns: true if the vector has no elements; false otherwise.

lastElement

public final synchronized Object lastElement()
This method retrieves the last element in the vector. If the vector is empty an exception is thrown.
Returns: The element at the specified zero-based index.
Throws: NoSuchElementException if the vector is empty.

lastIndexOf

public final int lastIndexOf(Object elem)
This method searches the vector and returns the zero-based index number of the last matching object.
Parameters: elem-the element to find the index of.
Returns: The element number of the last element that matches elem, or -1 if no match is found.

lastIndexOf

public final synchronized int lastIndexOf(Object elem, int index)
This method finds the last element in the vector that matches elem starting at the element given by index. It is very useful for traversing a vector backward searching for all elements matching a specific object.
Parameters:
elem-the element to find the last index of.
index-the index number at which to start the search.
Returns: The element number of the last element that matches elem, or -1 if no match is found.

removeAllElements

public final synchronized void removeAllElements()
This method can be used to remove all elements from the vector.

removeElement

public final synchronized boolean removeElement(Object obj)
This method can be used to remove a specific element from the vector. Only the first element that matches obj is removed.
Parameters: obj-the object to remove.
Returns: true if the element was found and deleted; false otherwise.

removeElementAt

public final synchronized void removeElementAt(int index)
This method removes the element at the specified zero-based index.
Parameters: index-the index number of the element to remove from the vector.
Throws: ArrayIndexOutOfBoundsException if the specified index is invalid.

setElementAt

public final synchronized void setElementAt(Object obj, int index)
This method replaces an element in the vector with another element.
Parameters:
obj-the object to be placed in the vector.
index-the index number of the element to be replaced.
Throws: ArrayIndexOutOfBoundsException if the specified index is invalid.

setSize

public final synchronized void setSize(int newSize)
This method sets the size of the vector. If the specified size makes the vector too small to hold its current elements, elements from the end of the vector are removed. If the new size is larger than the current size, empty elements are added at the end of the vector.
Parameters: newSize-the desired size of the vector.

size

public final int size()
The method returns the number of elements currently in the vector.
Returns: The number of elements in the vector.

toString

public final synchronized String toString()
This method overrides the toString method in Object and formats the contents of the vector as a string.
Returns: A string representation of the vector.

trimToSize

public final synchronized void trimToSize()
This method will remove any excess capacity from the vector by resizing it to hold only the quantity of elements it currently holds. If new items are added, the size of the vector will be increased.

EmptyStackException

Extends: RuntimeException
This exception signals when the stack is empty.

NoSuchElementException

Extends: RuntimeException
This exception signals when an enumeration is empty.