java.lang.Object java.lang.Number java.lang.Integer
The Integer class wraps a value of the primitive type int in an object. An object of type Integer contains a single field whose type is int.
In addition, this class provides several methods for converting an int to a String and a String to an int, as well as other constants and methods useful when dealing with an int.
Implementation note: The implementations of the "bit twiddling" methods (such as @link{#highestOneBit(int)} and @link{#numberOfTrailingZeros(int)}) are based on material from Henry S. Warren, Jr.'s Hacker's Delight , (Addison Wesley, 2002).
Field Summary  

static int 
MAX_VALUE
A constant holding the maximum value an int can have, 2^{ 31} 1. 
static int 
MIN_VALUE
A constant holding the minimum value an int can have, 2^{ 31} . 
static int 
SIZE
The number of bits used to represent an int value in two's complement binary form. 


static Class < Integer 
TYPE
The Class instance representing the primitive type int. 
Constructor Summary  

Integer
(int value) Constructs a newly allocated Integer object that represents the specified int value. 

Integer
(
String
s) Constructs a newly allocated Integer object that represents the int value indicated by the String parameter. 
Method Summary  

static int 
bitCount
(int i)
Returns the number of onebits in the two's complement binary representation of the specified int value. 
byte 
byteValue
() Returns the value of this Integer as a byte. 
int 
compareTo
(
Integer
anotherInteger) Compares two Integer objects numerically. 


static Integer 
decode
(
String
nm) Decodes a String into an Integer. 
double 
doubleValue
() Returns the value of this Integer as a double. 
boolean 
equals
(
Object
obj) Compares this object to the specified object. 
float 
floatValue
() Returns the value of this Integer as a float. 
static Integer 
getInteger
(
String
nm) Determines the integer value of the system property with the specified name. 
static Integer 
getInteger
(
String
nm, int val) Determines the integer value of the system property with the specified name. 
static Integer 
getInteger
(
String
nm,
Integer
val) Returns the integer value of the system property with the specified name. 
int 
hashCode
() Returns a hash code for this Integer. 
static int 
highestOneBit
(int i)
Returns an int value with at most a single onebit, in the position of the highestorder ("leftmost") onebit in the specified int value. 
int 
intValue
() Returns the value of this Integer as an int. 
long 
longValue
() Returns the value of this Integer as a long. 
static int 
lowestOneBit
(int i)
Returns an int value with at most a single onebit, in the position of the lowestorder ("rightmost") onebit in the specified int value. 
static int 
numberOfLeadingZeros
(int i)
Returns the number of zero bits preceding the highestorder ("leftmost") onebit in the two's complement binary representation of the specified int value. 
static int 
numberOfTrailingZeros
(int i)
Returns the number of zero bits following the lowestorder ("rightmost") onebit in the two's complement binary representation of the specified int value. 
static int 
parseInt
(
String
s) Parses the string argument as a signed decimal integer. 
static int 
parseInt
(
String
s, int radix) Parses the string argument as a signed integer in the radix specified by the second argument. 
static int 
reverse
(int i)
Returns the value obtained by reversing the order of the bits in the two's complement binary representation of the specified int value. 
static int 
reverseBytes
(int i)
Returns the value obtained by reversing the order of the bytes in the two's complement representation of the specified int value. 
static int 
rotateLeft
(int i, int distance)
Returns the value obtained by rotating the two's complement binary representation of the specified int value left by the specified number of bits. 
static int 
rotateRight
(int i, int distance)
Returns the value obtained by rotating the two's complement binary representation of the specified int value right by the specified number of bits. 
short 
shortValue
() Returns the value of this Integer as a short. 
static int 
signum
(int i)
Returns the signum function of the specified int value. 
static String 
toBinaryString
(int i) Returns a string representation of the integer argument as an unsigned integer in base 2. 
static String 
toHexString
(int i) Returns a string representation of the integer argument as an unsigned integer in base 16. 
static String 
toOctalString
(int i) Returns a string representation of the integer argument as an unsigned integer in base 8. 
String 
toString
() Returns a String object representing this Integer's value. 
static String 
toString
(int i) Returns a String object representing the specified integer. 
static String 
toString
(int i, int radix) Returns a string representation of the first argument in the radix specified by the second argument. 
static Integer 
valueOf
(int i)
Returns a Integer instance representing the specified int value. 
static Integer 
valueOf
(
String
s) Returns an Integer object holding the value of the specified String. 
static Integer 
valueOf
(
String
s, int radix) Returns an Integer object holding the value extracted from the specified String when parsed with the radix given by the second argument. 
Methods inherited from class java.lang. Object 

clone , finalize , getClass , notify , notifyAll , wait , wait , wait 
Methods inherited from interface java.lang. Comparable 

compareTo 
Field Detail 

public static final int MIN_VALUE
public static final int MAX_VALUE
public static final Class< Integer> TYPE
public static final int SIZE
Constructor Detail 

public Integer(int value)
public Integer(String s) throws NumberFormatException
Method Detail 

public static String toString(int i, int radix)
If the radix is smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX, then the radix 10 is used instead.
If the first argument is negative, the first element of the result is the ASCII minus character '' ('\u002D'). If the first argument is not negative, no sign character appears in the result.
The remaining characters of the result represent the magnitude of the first argument. If the magnitude is zero, it is represented by a single zero character '0' ('\u0030'); otherwise, the first character of the representation of the magnitude will not be the zero character. The following ASCII characters are used as digits:
These are '\u0030' through '\u0039' and '\u0061' through '\u007A'. If radix is N, then the first N of these characters are used as radixN digits in the order shown. Thus, the digits for hexadecimal (radix 16) are 0123456789abcdef. If uppercase letters are desired, the String.toUpperCase() method may be called on the result:0123456789abcdefghijklmnopqrstuvwxyz
Integer.toString(n, 16).toUpperCase()
public static String toHexString(int i)
The unsigned integer value is the argument plus 2^{ 32} if the argument is negative; otherwise, it is equal to the argument. This value is converted to a string of ASCII digits in hexadecimal (base 16) with no extra leading 0s. If the unsigned magnitude is zero, it is represented by a single zero character '0' ('\u0030'); otherwise, the first character of the representation of the unsigned magnitude will not be the zero character. The following characters are used as hexadecimal digits:
These are the characters '\u0030' through '\u0039' and '\u0061' through '\u0066'. If uppercase letters are desired, the String.toUpperCase() method may be called on the result:0123456789abcdef
Integer.toHexString(n).toUpperCase()
public static String toOctalString(int i)
The unsigned integer value is the argument plus 2^{ 32} if the argument is negative; otherwise, it is equal to the argument. This value is converted to a string of ASCII digits in octal (base 8) with no extra leading 0s.
If the unsigned magnitude is zero, it is represented by a single zero character '0' ('\u0030'); otherwise, the first character of the representation of the unsigned magnitude will not be the zero character. The following characters are used as octal digits:
These are the characters '\u0030' through '\u0037'.01234567
public static String toBinaryString(int i)
The unsigned integer value is the argument plus 2^{ 32} if the argument is negative; otherwise it is equal to the argument. This value is converted to a string of ASCII digits in binary (base 2) with no extra leading 0s. If the unsigned magnitude is zero, it is represented by a single zero character '0' ('\u0030'); otherwise, the first character of the representation of the unsigned magnitude will not be the zero character. The characters '0' ('\u0030') and '1' ('\u0031') are used as binary digits.
public static String toString(int i)
public static int parseInt(String s, int radix) throws NumberFormatException
An exception of type NumberFormatException is thrown if any of the following situations occurs:
Examples:
parseInt("0", 10) returns 0 parseInt("473", 10) returns 473 parseInt("0", 10) returns 0 parseInt("FF", 16) returns 255 parseInt("1100110", 2) returns 102 parseInt("2147483647", 10) returns 2147483647 parseInt("2147483648", 10) returns 2147483648 parseInt("2147483648", 10) throws a NumberFormatException parseInt("99", 8) throws a NumberFormatException parseInt("Kona", 10) throws a NumberFormatException parseInt("Kona", 27) returns 411787
public static int parseInt(String s) throws NumberFormatException
public static Integer valueOf(String s, int radix) throws NumberFormatException
In other words, this method returns an Integer object equal to the value of:
new Integer(Integer.parseInt(s, radix))
public static Integer valueOf(String s) throws NumberFormatException
In other words, this method returns an Integer object equal to the value of:
new Integer(Integer.parseInt(s))
public static IntegervalueOf (int i)
public byte byteValue()
public short shortValue()
public int intValue()
public long longValue()
public float floatValue()
public double doubleValue()
public String toString()
public int hashCode()
public boolean equals(Object obj)
public static Integer getInteger(String nm)
The first argument is treated as the name of a system property. System properties are accessible through the System.getProperty(java.lang.String) method. The string value of this property is then interpreted as an integer value and an Integer object representing this value is returned. Details of possible numeric formats can be found with the definition of getProperty.
If there is no property with the specified name, if the specified name is empty or null, or if the property does not have the correct numeric format, then null is returned.
In other words, this method returns an Integer object equal to the value of:
getInteger(nm, null)
public static Integer getInteger(String nm, int val)
The first argument is treated as the name of a system property. System properties are accessible through the System.getProperty(java.lang.String) method. The string value of this property is then interpreted as an integer value and an Integer object representing this value is returned. Details of possible numeric formats can be found with the definition of getProperty.
The second argument is the default value. An Integer object that represents the value of the second argument is returned if there is no property of the specified name, if the property does not have the correct numeric format, or if the specified name is empty or null.
In other words, this method returns an Integer object equal to the value of:
getInteger(nm, new Integer(val))but in practice it may be implemented in a manner such as:
to avoid the unnecessary allocation of an Integer object when the default value is not needed.Integer result = getInteger(nm, null); return (result == null) ? new Integer(val) : result;
public static Integer getInteger(String nm, Integer val)
The second argument is the default value. The default value is returned if there is no property of the specified name, if the property does not have the correct numeric format, or if the specified name is empty or null.
public static Integer decode(String nm) throws NumberFormatException
DecimalNumeral , HexDigits , and OctalDigits are defined in §3.10.1 of the Java Language Specification .
 DecodableString:
 Sign_{ opt} DecimalNumeral
 Sign_{ opt} 0x HexDigits
 Sign_{ opt} 0X HexDigits
 Sign_{ opt} # HexDigits
 Sign_{ opt} 0 OctalDigits
 Sign:
 
The sequence of characters following an (optional) negative sign and/or radix specifier ("0x", "0X", "#", or leading zero) is parsed as by the Integer.parseInt method with the indicated radix (10, 16, or 8). This sequence of characters must represent a positive value or a NumberFormatException will be thrown. The result is negated if first character of the specified String is the minus sign. No whitespace characters are permitted in the String.
public int compareTo(Integer anotherInteger)
public static int highestOneBitcompareTo(int i)(Objecto)
public static int lowestOneBit (int i)
public static int numberOfLeadingZeros (int i)
Note that this method is closely related to the logarithm base 2. For all positive int values x:
public static int numberOfTrailingZeros (int i)
public static int bitCount (int i)
public static int rotateLeft (int i, int distance)
Note that left rotation with a negative distance is equivalent to right rotation: rotateLeft(val, distance) == rotateRight(val, distance) . Note also that rotation by any multiple of 32 is a noop, so all but the last five bits of the rotation distance can be ignored, even if the distance is negative: rotateLeft(val, distance) == rotateLeft(val, distance & 0x1F) .
public static int rotateRight (int i, int distance)
Note that right rotation with a negative distance is equivalent to left rotation: rotateRight(val, distance) == rotateLeft(val, distance) . Note also that rotation by any multiple of 32 is a noop, so all but the last five bits of the rotation distance can be ignored, even if the distance is negative: rotateRight(val, distance) == rotateRight(val, distance & 0x1F) .
public static int reverse (int i)
public static int signum (int i)
public static int reverseBytes (int i)