Long (Java 2 Platform SE v1.4.1) - JDK 5 Documentation v1.4.1, Java 2 SDK 英文文档

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java.lang
Class Long

java.lang.Object
  |
  +--java.lang.Number
        |
        +--java.lang.Long

All Implemented Interfaces:: Comparable, Serializable

public final class Long
extends Number
implements Comparable

The Long class wraps a value of the primitive type long in an object. An object of type Long contains a single field whose type is long.

In addition, this class provides several methods for converting a long to a String and a String to a long, as well as other constants and methods useful when dealing with a long.

Since:: JDK1.0
See Also:: Serialized Form

Field Summary

static long MAX_VALUE
          A constant holding the maximum value a long can have, 2⁶³-1.

static long MIN_VALUE
          A constant holding the minimum value a long can have, -2⁶³.

static Class TYPE
          The Class instance representing the primitive type long.

Constructor Summary

Long(long value)
          Constructs a newly allocated Long object that represents the specified long argument.

Long(String s)
          Constructs a newly allocated Long object that represents the long value indicated by the String parameter.

Method Summary

byte byteValue()
          Returns the value of this Long as a byte.

int compareTo(Long anotherLong)
          Compares two Long objects numerically.

int compareTo(Object o)
          Compares this Long object to another object.

static Long decode(String nm)
          Decodes a String into a Long.

double doubleValue()
          Returns the value of this Long as a double.

boolean equals(Object obj)
          Compares this object to the specified object.

float floatValue()
          Returns the value of this Long as a float.

static Long getLong(String nm)
          Determines the long value of the system property with the specified name.

static Long getLong(String nm, long val)
          Determines the long value of the system property with the specified name.

static Long getLong(String nm, Long val)
          Returns the long value of the system property with the specified name.

int hashCode()
          Returns a hash code for this Long.

int intValue()
          Returns the value of this Long as an int.

long longValue()
          Returns the value of this Long as a long value.

static long parseLong(String s)
          Parses the string argument as a signed decimal long.

static long parseLong(String s, int radix)
          Parses the string argument as a signed long in the radix specified by the second argument.

short shortValue()
          Returns the value of this Long as a short.

static String toBinaryString(long i)
          Returns a string representation of the long argument as an unsigned integer in base 2.

static String toHexString(long i)
          Returns a string representation of the long argument as an unsigned integer in base 16.

static String toOctalString(long i)
          Returns a string representation of the long argument as an unsigned integer in base 8.

String toString()
          Returns a String object representing this Long's value.

static String toString(long i)
          Returns a String object representing the specified long.

static String toString(long i, int radix)
          Returns a string representation of the first argument in the radix specified by the second argument.

static Long valueOf(String s)
          Returns a Long object holding the value of the specified String.

static Long valueOf(String s, int radix)
          Returns a Long 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

Field Detail

MIN_VALUE

public static final long MIN_VALUE

A constant holding the minimum value a long can have, -2⁶³.

See Also:: Constant Field Values

MAX_VALUE

public static final long MAX_VALUE

A constant holding the maximum value a long can have, 2⁶³-1.

See Also:: Constant Field Values

TYPE

public static final Class TYPE

The Class instance representing the primitive type long.

Since:: JDK1.1

Constructor Detail

Long

public Long(long value)

Constructs a newly allocated Long object that represents the specified long argument.
Parameters:: value - the value to be represented by the Long object.

Long

public Long(String s)
     throws NumberFormatException

Constructs a newly allocated Long object that represents the long value indicated by the String parameter. The string is converted to a long value in exactly the manner used by the parseLong method for radix 10.
Parameters:: s - the String to be converted to a Long.
Throws:: NumberFormatException - if the String does not contain a parsable long.
See Also:: parseLong(java.lang.String, int)

Method Detail

toString

public static String toString(long i,
                              int radix)

Returns a string representation of the first argument in the radix specified by the second 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 sign '-' ('\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

These are '\u0030' through '\u0039' and '\u0061' through '\u007a'. If radix is N, then the first N of these characters are used as radix-N 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:

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

Parameters:: i - a longto be converted to a string.; radix - the radix to use in the string representation.
Returns:: a string representation of the argument in the specified radix.
See Also:: Character.MAX_RADIX, Character.MIN_RADIX

toHexString

public static String toHexString(long i)

Returns a string representation of the long argument as an unsigned integer in base 16.

The unsigned long value is the argument plus 2⁶⁴ 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:

 0123456789abcdef

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:

 Long.toHexString(n).toUpperCase()

Parameters:: i - a long to be converted to a string.
Returns:: the string representation of the unsigned long value represented by the argument in hexadecimal (base 16).
Since:: JDK 1.0.2

toOctalString

public static String toOctalString(long i)

Returns a string representation of the long argument as an unsigned integer in base 8.

The unsigned long value is the argument plus 2⁶⁴ 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:

01234567

These are the characters '\u0030' through '\u0037'.

Parameters:: i - a long to be converted to a string.
Returns:: the string representation of the unsigned long value represented by the argument in octal (base 8).
Since:: JDK 1.0.2

toBinaryString

public static String toBinaryString(long i)

Returns a string representation of the long argument as an unsigned integer in base 2.

The unsigned long value is the argument plus 2⁶⁴ 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.

Parameters:: i - a long to be converted to a string.
Returns:: the string representation of the unsigned long value represented by the argument in binary (base 2).
Since:: JDK 1.0.2

toString

public static String toString(long i)

Returns a String object representing the specified long. The argument is converted to signed decimal representation and returned as a string, exactly as if the argument and the radix 10 were given as arguments to the toString(long, int) method.

Parameters:: i - a long to be converted.
Returns:: a string representation of the argument in base 10.

parseLong

public static long parseLong(String s,
                             int radix)
                      throws NumberFormatException

Parses the string argument as a signed long in the radix specified by the second argument. The characters in the string must all be digits of the specified radix (as determined by whether Character.digit(char, int) returns a nonnegative value), except that the first character may be an ASCII minus sign '-' ('\u002D') to indicate a negative value. The resulting long value is returned.

Note that neither the character L ('\u004C') nor l ('\u006C') is permitted to appear at the end of the string as a type indicator, as would be permitted in Java programming language source code - except that either L or l may appear as a digit for a radix greater than 22.

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 Character.MIN_RADIX or larger than 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') provided that the string is longer than length 1.
The value represented by the string is not a value of type long.

Examples:

 parseLong("0", 10) returns 0L
 parseLong("473", 10) returns 473L
 parseLong("-0", 10) returns 0L
 parseLong("-FF", 16) returns -255L
 parseLong("1100110", 2) returns 102L
 parseLong("99", 8) throws a NumberFormatException
 parseLong("Hazelnut", 10) throws a NumberFormatException
 parseLong("Hazelnut", 36) returns 1356099454469L

Parameters:: s - the String containing the long representation to be parsed.; radix - the radix to be used while parsing s.
Returns:: the long represented by the string argument in the specified radix.
Throws:: NumberFormatException - if the string does not contain a parsable long.

parseLong

public static long parseLong(String s)
                      throws NumberFormatException

Parses the string argument as a signed decimal long. The characters in the string must all be decimal digits, except that the first character may be an ASCII minus sign '-' (\u002D') to indicate a negative value. The resulting long value is returned, exactly as if the argument and the radix 10 were given as arguments to the parseLong(java.lang.String, int) method.

Parameters:: s - a String containing the long representation to be parsed
Returns:: the long represented by the argument in decimal.
Throws:: NumberFormatException - if the string does not contain a parsable long.

valueOf

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

Returns a Long object holding the value extracted from the specified String when parsed with the radix given by the second argument. The first argument is interpreted as representing a signed long in the radix specified by the second argument, exactly as if the arguments were given to the parseLong(java.lang.String, int) method. The result is a Long object that represents the long value specified by the string.

In other words, this method returns a Long object equal to the value of:

new Long(Long.parseLong(s, radix))

Parameters:: s - the string to be parsed; radix - the radix to be used in interpreting s
Returns:: a Long object holding the value represented by the string argument in the specified radix.
Throws:: NumberFormatException - If the String does not contain a parsable long.

valueOf

public static Long valueOf(String s)
                    throws NumberFormatException

Returns a Long object holding the value of the specified String. The argument is interpreted as representing a signed decimal long, exactly as if the argument were given to the parseLong(java.lang.String) method. The result is a Long object that represents the integer value specified by the string.

In other words, this method returns a Long object equal to the value of:

 new Long(Long.parseLong(s))

Parameters:: s - the string to be parsed.
Returns:: a Long object holding the value represented by the string argument.
Throws:: NumberFormatException - If the string cannot be parsed as a long.

decode

public static Long decode(String nm)
                   throws NumberFormatException

Decodes a String into a Long. Accepts decimal, hexadecimal, and octal numbers given by the following grammar:

DecodableString:
Sign_opt DecimalNumeral
Sign_opt 0x HexDigits
Sign_opt 0X HexDigits
Sign_opt # HexDigits
Sign_opt 0 OctalDigits

Sign:
-

DecimalNumeral, HexDigits, and OctalDigits are defined in §3.10.1 of the Java Language Specification.

The sequence of characters following an (optional) negative sign and/or radix specifier ("0x", "0X", "#", or leading zero) is parsed as by the Long.parseLong 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.
Returns:: a Long object holding the long value represented by nm
Throws:: NumberFormatException - if the String does not contain a parsable long.
Since:: 1.2
See Also:: parseLong(String, int)

byteValue

public byte byteValue()

Returns the value of this Long as a byte.

Overrides:: byteValue in class Number

Returns:: the numeric value represented by this object after conversion to type byte.

shortValue

public short shortValue()

Returns the value of this Long as a short.

Overrides:: shortValue in class Number

Returns:: the numeric value represented by this object after conversion to type short.

intValue

public int intValue()

Returns the value of this Long as an int.

Specified by:: intValue in class Number

Returns:: the numeric value represented by this object after conversion to type int.

longValue

public long longValue()

Returns the value of this Long as a long value.

Specified by:: longValue in class Number

Returns:: the numeric value represented by this object after conversion to type long.

floatValue

public float floatValue()

Returns the value of this Long as a float.

Specified by:: floatValue in class Number

Returns:: the numeric value represented by this object after conversion to type float.

doubleValue

public double doubleValue()

Returns the value of this Long as a double.

Specified by:: doubleValue in class Number

Returns:: the numeric value represented by this object after conversion to type double.

toString

public String toString()

Returns a String object representing this Long's value. The value is converted to signed decimal representation and returned as a string, exactly as if the long value were given as an argument to the toString(long) method.

Overrides:: toString in class Object

Returns:: a string representation of the value of this object in base 10.

hashCode

public int hashCode()

Returns a hash code for this Long. The result is the exclusive OR of the two halves of the primitive long value held by this Long object. That is, the hashcode is the value of the expression:

 (int)(this.longValue()^(this.longValue()>>>32))

Overrides:: hashCode in class Object

Returns:: a hash code value for this object.
See Also:: Object.equals(java.lang.Object), Hashtable

equals

public boolean equals(Object obj)

Compares this object to the specified object. The result is true if and only if the argument is not null and is a Long object that contains the same long value as this object.

Overrides:: equals in class Object

Parameters:: obj - the object to compare with.
Returns:: true if the objects are the same; false otherwise.
See Also:: Object.hashCode(), Hashtable

getLong

public static Long getLong(String nm)

Determines the long value of the system property with the specified name.

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 a long value and a Long 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 a Long object equal to the value of:

getLong(nm, null)

Parameters:: nm - property name.
Returns:: the Long value of the property.
See Also:: System.getProperty(java.lang.String), System.getProperty(java.lang.String, java.lang.String)

getLong

public static Long getLong(String nm,
                           long val)

Determines the long value of the system property with the specified name.

The second argument is the default value. A Long 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 a Long object equal to the value of:

getLong(nm, new Long(val))

but in practice it may be implemented in a manner such as:

 Long result = getLong(nm, null);
 return (result == null) ? new Long(val) : result;

to avoid the unnecessary allocation of a Long object when the default value is not needed.

Parameters:: nm - property name.; val - default value.
Returns:: the Long value of the property.
See Also:: System.getProperty(java.lang.String), System.getProperty(java.lang.String, java.lang.String)

getLong

public static Long getLong(String nm,
                           Long val)

Returns the long value of the system property with the specified name. 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 a long value, as per the Long.decode method, and a Long object representing this value is returned.

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 for the method 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 valueOf(java.lang.String, int) with radix 8.
Otherwise the property value is parsed as a decimal integer exactly as by the method valueOf(java.lang.String, int) with radix 10.

Note that, in every case, neither L ('\u004C') nor l ('\u006C') is permitted to appear at the end of the property value as a type indicator, as would be permitted in Java programming language source code.

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.; val - default value.
Returns:: the Long value of the property.
See Also:: System.getProperty(java.lang.String), System.getProperty(java.lang.String, java.lang.String), decode(java.lang.String)

compareTo

public int compareTo(Long anotherLong)

Compares two Long objects numerically.

Parameters:: anotherLong - the Long to be compared.
Returns:: the value 0 if this Long is equal to the argument Long; a value less than 0 if this Long is numerically less than the argument Long; and a value greater than 0 if this Long is numerically greater than the argument Long (signed comparison).
Since:: 1.2

compareTo

public int compareTo(Object o)

Compares this Long object to another object. If the object is a Long, this function behaves like compareTo(Long). Otherwise, it throws a ClassCastException (as Long objects are comparable only to other Long objects).

Specified by:: compareTo in interface Comparable

Parameters:: o - the Object to be compared.
Returns:: the value 0 if the argument is a Long numerically equal to this Long; a value less than 0 if the argument is a Long numerically greater than this Long; and a value greater than 0 if the argument is a Long numerically less than this Long.
Throws:: ClassCastException - if the argument is not a Long.
Since:: 1.2
See Also:: Comparable

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Field Summary
`static long`	`MAX_VALUE` A constant holding the maximum value a `long` can have, 2⁶³-1.
`static long`	`MIN_VALUE` A constant holding the minimum value a `long` can have, -2⁶³.
`static Class`	`TYPE` The `Class` instance representing the primitive type `long`.

Constructor Summary
`Long(long value)` Constructs a newly allocated `Long` object that represents the specified `long` argument.
`Long(String s)` Constructs a newly allocated `Long` object that represents the `long` value indicated by the `String` parameter.

Method Summary
`byte`	`byteValue()` Returns the value of this `Long` as a `byte`.
`int`	`compareTo(Long anotherLong)` Compares two `Long` objects numerically.
`int`	`compareTo(Object o)` Compares this `Long` object to another object.
`static Long`	`decode(String nm)` Decodes a `String` into a `Long`.
`double`	`doubleValue()` Returns the value of this `Long` as a `double`.
`boolean`	`equals(Object obj)` Compares this object to the specified object.
`float`	`floatValue()` Returns the value of this `Long` as a `float`.
`static Long`	`getLong(String nm)` Determines the `long` value of the system property with the specified name.
`static Long`	`getLong(String nm, long val)` Determines the `long` value of the system property with the specified name.
`static Long`	`getLong(String nm, Long val)` Returns the `long` value of the system property with the specified name.
`int`	`hashCode()` Returns a hash code for this `Long`.
`int`	`intValue()` Returns the value of this `Long` as an `int`.
`long`	`longValue()` Returns the value of this `Long` as a `long` value.
`static long`	`parseLong(String s)` Parses the string argument as a signed decimal `long`.
`static long`	`parseLong(String s, int radix)` Parses the string argument as a signed `long` in the radix specified by the second argument.
`short`	`shortValue()` Returns the value of this `Long` as a `short`.
`static String`	`toBinaryString(long i)` Returns a string representation of the `long` argument as an unsigned integer in base 2.
`static String`	`toHexString(long i)` Returns a string representation of the `long` argument as an unsigned integer in base 16.
`static String`	`toOctalString(long i)` Returns a string representation of the `long` argument as an unsigned integer in base 8.
`String`	`toString()` Returns a `String` object representing this `Long`'s value.
`static String`	`toString(long i)` Returns a `String` object representing the specified `long`.
`static String`	`toString(long i, int radix)` Returns a string representation of the first argument in the radix specified by the second argument.
`static Long`	`valueOf(String s)` Returns a `Long` object holding the value of the specified `String`.
`static Long`	`valueOf(String s, int radix)` Returns a `Long` object holding the value extracted from the specified `String` when parsed with the radix given by the second argument.

Long (Java 2 Platform SE v1.4.1) - JDK 5 Documentation v1.4.1, Java 2 SDK 英文文档

java.lang Class Long

MIN_VALUE

MAX_VALUE

TYPE

Long

Long

toString

toHexString

toOctalString

toBinaryString

toString

parseLong

parseLong

valueOf

valueOf

decode

byteValue

shortValue

intValue

longValue

floatValue

doubleValue

toString

hashCode

equals

getLong

getLong

getLong

compareTo

compareTo

java.lang
Class Long