Java Doc for Integer.java in  » 6.0-JDK-Core » lang » java » lang » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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 Integer.highestOneBit(int) highestOneBit and Integer.numberOfTrailingZeros(int) numberOfTrailingZeros ) are based on material from Henry S. Warren, Jr.'s Hacker's Delight, (Addison Wesley, 2002).
author:
   Lee Boynton
author:
   Arthur van Hoff
author:
   Josh Bloch
author:
   Joseph D. Darcy
version:
   1.102, 07/12/07
since:
   JDK1.0

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 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).

The first argument is treated as the name of a system property.

The first argument is treated as the name of a system property. System properties are accessible through the java.lang.System.getProperty(java.lang.String) method.

The unsigned integer value is the argument plus 2³² if the argument is negative; otherwise it is equal to the argument.

The unsigned integer value is the argument plus 2³² if the argument is negative; otherwise, it is equal to the argument.

The unsigned integer value is the argument plus 2³² if the argument is negative; otherwise, it is equal to the argument.

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').

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 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 .
Parameters:
  nm - the String to decode. an Integer object holding the int value represented by nm
exception:
  NumberFormatException - if the String does notcontain a parsable integer.
See Also:   java.lang.Integer.parseInt(java.lang.Stringint)

The first argument is treated as the name of a system property. System properties are accessible through the java.lang.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)

The first argument is treated as the name of a system property. System properties are accessible through the java.lang.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))

 Integer result = getInteger(nm, null);
 return (result == null) ? new Integer(val) : result;
 

• If the property value begins with the two ASCII characters 0x or the ASCII character # , not followed by a minus sign, then the rest of it is parsed as a hexadecimal integer exactly as by the method Integer.valueOf(java.lang.String,int) with radix 16.
• If the property value begins with the ASCII character 0 followed by another character, it is parsed as an octal integer exactly as by the method Integer.valueOf(java.lang.String,int) with radix 8.
• Otherwise, the property value is parsed as a decimal integer exactly as by the method Integer.valueOf(java.lang.String,int) with radix 10.

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 .
Parameters:
  nm - property name.
Parameters:
  val - default value. the Integer value of the property.
See Also:   java.lang.System.getProperty(java.lang.String)
See Also:   java.lang.System.getProperty(java.lang.Stringjava.lang.String)
See Also:   java.lang.Integer.decode

Note that this method is closely related to the logarithm base 2. For all positive int values x:

• floor(log₂(x)) = 31 - numberOfLeadingZeros(x)
• ceil(log₂(x)) = 32 - numberOfLeadingZeros(x - 1)

An exception of type NumberFormatException is thrown if any of the following situations occurs:

• The first argument is null or is a string of length zero.
• The radix is either smaller than java.lang.Character.MIN_RADIX or larger than java.lang.Character.MAX_RADIX .
• Any character of the string is not a digit of the specified radix, except that the first character may be a minus sign '-' ('\u002D') or plus sign '+' ('\u002B') provided that the string is longer than length 1.
• The value represented by the string is not a value of type int .

Examples:

 parseInt("0", 10) returns 0
 parseInt("473", 10) returns 473
 parseInt("+42", 10) returns 42
 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
 

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 no-op, 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) . the value obtained by rotating the two's complement binaryrepresentation of the specified int value left by thespecified number of bits.
since:
   1.5

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 no-op, 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) . the value obtained by rotating the two's complement binaryrepresentation of the specified int value right by thespecified number of bits.
since:
   1.5

The unsigned integer value is the argument plus 2³² 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 0 s. 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.
Parameters:
  i - an integer to be converted to a string. the string representation of the unsigned integer valuerepresented by the argument in binary (base 2).
since:
   JDK1.0.2

The unsigned integer value is the argument plus 2³² 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 0 s. 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:

0123456789abcdef

Integer.toHexString(n).toUpperCase()

The unsigned integer value is the argument plus 2³² 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 0 s.

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:

01234567

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:

0123456789abcdefghijklmnopqrstuvwxyz

Integer.toString(n, 16).toUpperCase()

In other words, this method returns an Integer object equal to the value of:

new Integer(Integer.parseInt(s, radix))

In other words, this method returns an Integer object equal to the value of:

new Integer(Integer.parseInt(s))