Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class Long - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

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java.lang
Class Long

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

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
          The largest value of type long.

static long MIN_VALUE
          The smallest value of type long.

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

Constructor Summary

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

Long(String s)
          Constructs a newly allocated Long object that represents the value represented by the string in decimal form.

Method Summary

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

int compareTo(Long anotherLong)
          Compares two Longs numerically.

int compareTo(Object o)
          Compares this Long 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 against 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()
          Computes a hashcode 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)
          Creates a string representation of the long argument as an unsigned integer in base 2.

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

static String toOctalString(long i)
          Creates 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 new String object representing the specified integer.

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

static Long valueOf(String s)
          Returns a new long object initialized to the value of the specified String.

static Long valueOf(String s, int radix)
          Returns a new long object initialized to the value of the specified String.

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

The smallest value of type long.

MAX_VALUE

public static final long MAX_VALUE

The largest value of type long.

TYPE

public static final Class TYPE

The Class object representing the primitive type long.

Since:: JDK1.1

Constructor Detail

Long

public Long(long value)

Constructs a newly allocated Long object that represents the primitive 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 value represented by the string in decimal form. The string is converted to an long value as if by the parseLong(java.lang.String, int) 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 integer.
See Also:: valueOf(java.lang.String)

Method Detail

toString

public static String toString(long i,
                              int radix)

Creates 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 the 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 long.; radix - the radix.
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)

Creates 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.

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.
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)

Creates 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.

01234567

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

Parameters:: i - a long.
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)

Creates 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.

If the unsigned magnitude is zero, it is represented by a single zero character '0' ('&392;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.
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 new String object representing the specified integer. 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(java.lang.String, int) method that takes two arguments.

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 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 L nor l 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.
The first character of the string is not a digit of the specified radix and is not a minus sign '-' ('\u002d').
The first character of the string is a minus sign and the string is of length 1.
Any character of the string after the first is not a digit of the specified radix.
The integer value represented by the string cannot be represented as 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.; radix - the radix to be used.
Returns:: the long represented by the string argument in the specified radix.
Throws:: NumberFormatException - if the string does not contain a parsable integer.

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(String, int) method that takes two arguments.

Note that neither L nor l is permitted to appear at the end of the string as a type indicator, as would be permitted in Java programming language source code.

Parameters:: s - a string.
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 new long object initialized to the value of the specified String. Throws an exception if the String cannot be parsed as a long.

The first argument is interpreted as representing a signed integer in the radix specified by the second argument, exactly as if the arguments were given to the parseLong(java.lang.String, int) method that takes two arguments. 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, radix))

Parameters:: s - the String containing the long.; radix - the radix to be used.
Returns:: a newly constructed Long initialized to 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 new long object initialized to the value of the specified String. Throws an exception if the String cannot be parsed as a long. The radix is assumed to be 10.

The argument is interpreted as representing a signed decimal integer, exactly as if the argument were given to the parseLong(java.lang.String) method that takes one argument). 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 newly constructed Long initialized to the value represented by the string argument.
Throws:: NumberFormatException - If the String does not contain a parsable long.

decode

public static Long decode(String nm)
                   throws NumberFormatException

Decodes a String into a Long. Accepts decimal, hexadecimal, and octal numbers, in the following formats:

     [-]    
     [-] 0x     
     [-] #      
     [-] 0

The constant following an (optional) negative sign and/or "radix specifier" is parsed as by the Long.parseLong method with the specified radix (10, 8 or 16). This constant must be positive or a NumberFormatException will result. The result is made negative if first character of the specified String is the negative sign. No whitespace characters are permitted in the String.

Parameters:: nm - the String to decode.
Returns:: the Long represented by the specified string.
Throws:: NumberFormatException - if the String does not contain a parsable long.
See Also:: parseLong(String, int)

byteValue

public byte byteValue()

Returns the value of this Long as a byte.

Overrides:: byteValue in class Number

Since:: JDK1.1

shortValue

public short shortValue()

Returns the value of this Long as a short.

Overrides:: shortValue in class Number

Since:: JDK1.1

intValue

public int intValue()

Returns the value of this Long as an int.

Overrides:: intValue in class Number

Returns:: the long value represented by this object is converted to type int and the result of the conversion is returned.

longValue

public long longValue()

Returns the value of this Long as a long value.

Overrides:: longValue in class Number

Returns:: the long value represented by this object.

floatValue

public float floatValue()

Returns the value of this Long as a float.

Overrides:: floatValue in class Number

Returns:: the long value represented by this object is converted to type float and the result of the conversion is returned.

doubleValue

public double doubleValue()

Returns the value of this Long as a double.

Overrides:: doubleValue in class Number

Returns:: the long value represented by this object that is converted to type double and the result of the conversion is returned.

toString

public String toString()

Returns a String object representing this Long's value. The long integer value represented by this Long object 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 that takes one argument.

Overrides:: toString in class Object

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

hashCode

public int hashCode()

Computes a hashcode for this Long. The result is the exclusive OR of the two halves of the primitive long value represented 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.

equals

public boolean equals(Object obj)

Compares this object against 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.

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, 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 first argument is treated as the name of a system property. System properties are accessible through the java.lang.System#getProperty() 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, or if the property does not have the correct numeric format, then a Long object that represents the value of the second argument is returned.

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 character 0 followed by another character, it is parsed as an octal integer exactly as for the method valueOf(java.lang.String, int) with radix 8.
Otherwise the property value is parsed as a decimal integer exactly as for the method valueOf(java.lang.String, int) with radix 10.
Note that, in every case, neither L nor l 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. If there is no property of the specified name, or if the property does not have the correct numeric format, then the second argument is returned.

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 Longs numerically.

Parameters:: anotherLong - the Long to be compared.
Returns:: the value 0 if the argument Long is equal to this Long; a value less than 0 if this Long is numerically less than the Long argument; and a value greater than 0 if this Long is numerically greater than the Long argument (signed comparison).
Since:: JDK1.2

compareTo

public int compareTo(Object o)

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

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:: JDK1.2
See Also:: Comparable

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Submit a bug or feature
Java, Java 2D, and JDBC are a trademarks or registered trademarks of Sun Microsystems, Inc. in the US and other countries.
Copyright 1993-1999 Sun Microsystems, Inc. 901 San Antonio Road,
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Field Summary
`static long`	`MAX_VALUE` The largest value of type `long`.
`static long`	`MIN_VALUE` The smallest value of type `long`.
`static Class`	`TYPE` The Class object representing the primitive type long.

Constructor Summary
`Long(long value)` Constructs a newly allocated `Long` object that represents the primitive `long` argument.
`Long(String s)` Constructs a newly allocated `Long` object that represents the value represented by the string in decimal form.

Method Summary
`byte`	`byteValue()` Returns the value of this Long as a byte.
`int`	`compareTo(Long anotherLong)` Compares two Longs numerically.
`int`	`compareTo(Object o)` Compares this Long 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 against 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()` Computes a hashcode 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)` Creates a string representation of the long argument as an unsigned integer in base 2.
`static String`	`toHexString(long i)` Creates a string representation of the long argument as an unsigned integer in base 16.
`static String`	`toOctalString(long i)` Creates 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 new String object representing the specified integer.
`static String`	`toString(long i, int radix)` Creates a string representation of the first argument in the radix specified by the second argument.
`static Long`	`valueOf(String s)` Returns a new long object initialized to the value of the specified String.
`static Long`	`valueOf(String s, int radix)` Returns a new long object initialized to the value of the specified String.

Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class Long - JDK 5 Documentation v1.2.2, 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