Chapter 10
The java.lang Package

Integer

Name

Integer

Synopsis

Class Name:

java.lang.Integer

Superclass:

java.lang.Number

Immediate Subclasses:

None

Interfaces Implemented:

None

Availability:

JDK 1.0 or later

The Integer class provides an object wrapper for an int value. This is useful when you need to treat an int value as an object. For example, there are a number of utility methods that take a reference to an Object as one of their arguments. You cannot specify an int value for one of these arguments, but you can provide a reference to an Integer object that encapsulates the int value. Also, as of JDK 1.1, the Integer class is necessary to support the Reflection API and class literals.

The Integer class also provides a number of utility methods for converting int values to other primitive types and for converting int values to strings and vice versa.

Class Summary

public final class java.lang.Integer extends java.lang.Number {
    // Constants
    public static final int MAX_VALUE;
    public static final int MIN_VALUE;
    public final static Class TYPE;                    // New in 1.1
    // Constructors
    public Integer(int value);
    public Integer(String s);
    // Class Methods
    public static Integer decode(String nm)            // New in 1.1
    public static Integer getInteger(String nm);
    public static Integer getInteger(String nm, int val);
    public static Integer getInteger(String nm, Integer val);
    public static int parseInt(String s);
    public static int parseInt(String s, int radix;
    public static String toBinaryString(long i);
    public static String toHexString(long i);
    public static String toOctalString(long i);
    public static String toString(int i);
    public static String toString(int i, int radix);
    public static Integer valueOf(String s);
    public static Integer valueOf(String s, int radix);
    // Instance Methods
    public byte byteValue();                           // New in 1.1
    public double doubleValue();
    public boolean equals(Object obj);
    public float floatValue();
    public int hashCode();
    public int intValue();
    public long longValue();
    public short shortValue();                         // New in 1.1
    public String toString();
}

Constants

MAX_VALUE

`public static final int MAX_VALUE = 0x7fffffff // 2147483647`

Description: The largest value that can be represented by an int.

MIN_VALUE

`public static final int MIN_VALUE = 0x80000000 // -2147483648`

Description: The smallest value that can be represented by an int.

TYPE

`public static final Class TYPE`

Availability

New as of JDK 1.1

Description

The Class object that represents the type int. It is always true that Integer.TYPE == int.class.

Constructors

Integer

`public Integer(int value)`

Parameters

value: The int value to be encapsulated by this object.

Description

Creates an Integer object with the specified int value.

`public Integer(String s) throws NumberFormatException`

Parameters

s: The string to be made into an Integer object.

Throws

NumberFormatException: If the sequence of characters in the given String does not form a valid int literal.

Description

Constructs an Integer object with the value specified by the given string. The string should consist of one or more digit characters. The digit characters can be preceded by a single `-' character. If the string contains any other characters, the constructor throws a NumberFormatException.

Class Methods

decode

`public static Integer decode(String nm)`

Availability

New as of JDK 1.1

Parameters

nm: A String representation of the value to be encapsulated by an Integer object. If the string begins with # or 0x, it is a radix 16 representation of the value. If the string begins with 0, it is a radix 8 representation of the value. Otherwise, it is assumed to be a radix 10 representation of the value.

Returns

An Integer object that encapsulates the given value.

Throws

NumberFormatException: If the String contains any nondigit characters other than a leading minus sign or the value represented by the String is less than Integer.MIN_VALUE or greater than Integer.MAX_VALUE.

Description

This method returns an Integer object that encapsulates the given value.

getInteger

`public static Integer getInteger(String nm)`

Parameters

nm: The name of a system property.

Returns

The value of the system property as an Integer object, or an Integer object with the value 0 if the named property does not exist or cannot be parsed.

Description

This method retrieves the value of the named system property and returns it as an Integer object. The method obtains the value of the system property as a String using System.getProperty().

If the value of the property begins with 0x or # and is not followed by a minus sign, the rest of the value is parsed as a hexadecimal integer. If the value begins with 0, it's parsed as an octal integer; otherwise it's parsed as a decimal integer.

`public static Integer getInteger(String nm, int val)`

Parameters

nm

The name of a system property.

val

A default int value for the property.

Returns

The value of the system property as an Integer object, or an Integer object with the value val if the named property does not exist or cannot be parsed.

Description

This method retrieves the value of the named system property and returns it as an Integer object. The method obtains the value of the system property as a String using System.getProperty().

`public static Integer getInteger(String nm, Integer val)`

Parameters

nm

The name of a system property.

val

A default Integer value for the property.

Returns

The value of the system property as an Integer object, or the Integer object val if the named property does not exist or cannot be parsed.

Description

This method retrieves the value of the named system property and returns it as an Integer object. The method obtains the value of the system property as a String using System.getProperty().

parseInt

 public static int parseInt(String s) throws NumberFormatException

Parameters

s: The String to be converted to an int value.

Returns

The numeric value of the integer represented by the String object.

Throws

NumberFormatException: If the String does not contain a valid representation of an integer.

Description

This method returns the numeric value of the integer represented by the contents of the given String object. The String must contain only decimal digits, except that the first character may be a minus sign.

 public static int parseInt(String s, int radix) throws NumberFormatException

Parameters

s

The String to be converted to an int value.

radix

The radix used in interpreting the characters in the String as digits. This value must be in the range Character.MIN_RADIX to Character.MAX_RADIX. If radix is in the range 2 through 10, only characters for which the Character.isDigit() method returns true are considered to be valid digits. If radix is in the range 11 through 36, characters in the ranges `A' through `Z' and `a' through `z' may be considered valid digits.

Returns

The numeric value of the integer represented by the String object in the specified radix.

Throws

NumberFormatException: If the String does not contain a valid representation of an integer, or radix is not in the appropriate range.

Description

This method returns the numeric value of the integer represented by the contents of the given String object in the specified radix. The String must contain only valid digits of the specified radix, except that the first character may be a minus sign. The digits are parsed in the specified radix to produce the numeric value.

toBinaryString

`public static String toBinaryString(int value)`

Parameters

value: The int value to be converted to a string.

Returns

A string that contains the binary representation of the given value.

Description

This method returns a String object that contains the representation of the given value as an unsigned binary number. To convert the given value to an unsigned quantity, the method simply uses the value as if it were not negative. In other words, if the given value is negative, the method adds 2^32 to it. Otherwise the value is used as it is.

The string returned by this method contains a sequence of one or more `0' and `1' characters. The method returns "0" if its argument is 0. Otherwise, the string returned by this method begins with `1'.

toHexString

`public static String toHexString(int value)`

Parameters

value: The int value to be converted to a string.

Returns

A string that contains the hexadecimal representation of the given value.

Description

This method returns a String object that contains the representation of the given value as an unsigned hexadecimal number. To convert the given value to an unsigned quantity, the method simply uses the value as if it were not negative. In other words, if the given value is negative, the method adds 2^32 to it. Otherwise the value is used as it is.

The string returned by this method contains a sequence of one or more of the characters `0', `1', `2', `3', `4', `5', `6', `7', `8', `9', `a', `b', `c', `d', `e', and `f'. The method returns "0" if its argument is 0. Otherwise, the string returned by this method does not begin with `0'.

To produce a string that contains upper- instead of lowercase letters, use the String.toUpperCase() method.

toOctalString

`public static String toOctalString(int value)`

Parameters

value: The int value to be converted to a string.

Returns

A string that contains the octal representation of the given value.

Description

This method returns a String object that contains a representation of the given value as an unsigned octal number. To convert the given value to an unsigned quantity, the method simply uses the value as if it were not negative. In other words, if the given value is negative, the method adds 2^32 to it. Otherwise the value is used as it is.

The string returned by this method contains a sequence of one or more of the characters `0', `1', `2', `3', `4', `5', `6', and `7'. The method returns "0" if its argument is 0. Otherwise, the string returned by this method does not begin with `0'.

toString

`public static String toString(int i)`

Parameters

i: The int value to be converted to a string.

Returns

The string representation of the given value.

Description

This method returns a String object that contains the decimal representation of the given value.

This method returns a string that begins with `-' if the given value is negative. The rest of the string is a sequence of one or more of the characters `0', `1', `2', `3', `4', `5', `6', `7', `8', and `9'. This method returns "0" if its argument is 0. Otherwise, the string returned by this method does not begin with "0" or "-0".

`public static String toString(int i, int radix)`

Parameters

i

The int value to be converted to a string.

radix

The radix used in converting the value to a string. This value must be in the range Character.MIN_RADIX to Character.MAX_RADIX.

Returns

The string representation of the given value in the specified radix.

Description

This method returns a String object that contains the representation of the given value in the specified radix.

This method returns a string that begins with `-' if the given value is negative. The rest of the string is a sequence of one or more characters that represent the magnitude of the given value. The characters that can appear in the sequence are determined by the value of radix. If N is the value of radix, the first N characters on the following line can appear in the sequence:

0123456789abcdefghijklmnopqrstuvwxyz

The method does not verify that radix is in the proper range. If radix is less than Character.MIN_RADIX or greater than Character.MAX_RADIX, the value 10 is used instead of the given value.

This method returns "0" if its argument is 0. Otherwise, the string returned by this method does not begin with "0" or "-0".

valueOf

 public static Integer valueOf(String s) throws NumberFormatException

Parameters

s: The string to be made into an Integer object.

Returns

The Integer object constructed from the string.

Throws

NumberFormatException: If the String does not contain a valid representation of an integer.

Description

 public static Integer valueOf(String s, int radix) throws NumberFormatException

Parameters

s

The string to be made into an Integer object.

radix

The radix used in converting the string to a value. This value must be in the range Character.MIN_RADIX to Character.MAX_RADIX.

Returns

The Integer object constructed from the string.

Throws

NumberFormatException: If the String does not contain a valid representation of an integer or radix is not in the appropriate range.

Description

Constructs an Integer object with the value specified by the given string in the specified radix. The string should consist of one or more digit characters or characters in the range `A' to `Z' or `a' to `z' that are considered digits in the given radix. The digit characters can be preceded by a single `-' character. If the string contains any other characters, the method throws a NumberFormatException.

Instance Methods

byteValue

`public byte byteValue()`

Availability

New as of JDK 1.1

Returns

The value of this object as a byte.

Overrides

Number.byteValue()

Description

This method returns the value of this object as a byte. The high order bits of the value are discarded.

doubleValue

`public double doubleValue()`

Returns

The value of this object as a double.

Overrides

Number.doubleValue()

Description

This method returns the value of this object as a double.

equals

`public boolean equals(Object obj)`

Parameters

obj: The object to be compared with this object.

Availability

New as of JDK 1.1

Returns

The value of this object as a short.

Overrides

Number.shortValue()

Description

This method returns the value of this object as a short. The high order bits of the value are discarded.

toString

`public String toString()`

Returns

The string representation of the value of this object.

Overrides

Object.toString()

Description

This method returns a String object that contains the decimal representation of the value of this object.

This method returns a string that begins with `-' if the value is negative. The rest of the string is a sequence of one or more of the characters `0', `1', `2', `3', `4', `5', `6', `7', `8', and `9'. This method returns "0" if the value of the object is 0. Otherwise, the string returned by this method does not begin with "0" or "-0".

Inherited Methods

Method	Inherited From	Method	Inherited From
`clone()`	`Object`	`finalize()`	`Object`
`getClass()`	`Object`	`notify()`	`Object`
`notifyAll()`	`Object`	`wait()`	`Object`
`wait(long)`	`Object`	`wait(long, int)`	`Object`