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Class java.lang.Long - JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档

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Class java.lang.Long 

java.lang.Object
   |
   +----java.lang.Number
           |
           +----java.lang.Long
public final class Long
extends Number
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.

Variable Index

o MAX_VALUE
The largest value of type long.
o MIN_VALUE
The smallest value of type long.
o TYPE
The Class object representing the primitive type long.

Constructor Index

o Long(long)
Constructs a newly allocated Long object that represents the primitive long argument.
o Long(String)
Constructs a newly allocated Long object that represents the value represented by the string.

Method Index

o byteValue()
Returns the value of this Long as a byte.
o doubleValue()
Returns the value of this Long as a double.
o equals(Object)
Compares this object against the specified object.
o floatValue()
Returns the value of this Long as a float.
o getLong(String)
Determines the long value of the system property with the specified name.
o getLong(String, Long)
Determines the long value of the system property with the specified name.
o getLong(String, long)
Determines the long value of the system property with the specified name.
o hashCode()
Computes a hashcode for this Long.
o intValue()
Returns the value of this Long as an int.
o longValue()
Returns the value of this Long as a long.
o parseLong(String)
Parses the string argument as a signed decimal long.
o parseLong(String, int)
Parses the string argument as a signed long in the radix specified by the second argument.
o shortValue()
Returns the value of this Long as a short.
o toBinaryString(long)
Creates a string representation of the long argument as an unsigned integer in base 2.
o toHexString(long)
Creates a string representation of the long argument as an unsigned integer in base 16.
o toOctalString(long)
Creates a string representation of the long argument as an unsigned integer in base 8.
o toString()
Returns a String object representing this Long's value.
o toString(long)
Returns a new String object representing the specified integer.
o toString(long, int)
Creates a string representation of the first argument in the radix specified by the second argument.
o valueOf(String)
Returns a new long object initialized to the value of the specified String.
o valueOf(String, int)
Returns a new long object initialized to the value of the specified String.

Variables

o MIN_VALUE 
 public static final long MIN_VALUE
The smallest value of type long.

o MAX_VALUE 
 public static final long MAX_VALUE
The largest value of type long.

o TYPE 
 public static final Class TYPE
The Class object representing the primitive type long.

Constructors

o 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.
o Long 
 public Long(String s) throws NumberFormatException
Constructs a newly allocated Long object that represents the value represented by the string. The string is converted to an long value as if by the valueOf method.

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

Methods

o 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 '-'. If the first argument is not negative, no sign character appears in the result. The following ASCII characters are used as digits:

    0123456789abcdefghijklmnopqrstuvwxyz

Parameters:
i - a long.
radix - the radix.
Returns:
a string representation of the argument in the specified radix.
See Also:
MAX_RADIX, MIN_RADIX
o 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. This value is converted to a string of ASCII digits in hexadecimal (base 16) with no extra leading 0s.

Parameters:
i - a long.
Returns:
the string representation of the unsigned long value represented by the argument in hexadecimal (base 16).
o 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. This value is converted to a string of ASCII digits in octal (base 8) with no extra leading 0s.

Parameters:
i - a long.
Returns:
the string representation of the unsigned long value represented by the argument in octal (base 8).
o 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. This value is converted to a string of ASCII digits in binary (base 2) with no extra leading 0s.

Parameters:
i - a long.
Returns:
the string representation of the unsigned long value represented by the argument in binary (base 2).
o toString 
 public static String toString(long i)
Returns a new String object representing the specified integer. The radix is assumed to be 10.

Parameters:
i - a long to be converted.
Returns:
a string representation of the argument in base 10.
o 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 '-' to indicate a negative value. The resulting long value is returned.

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.
o 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 '-' to indicate a negative value.

Parameters:
s - a string.
Returns:
the long represented by the argument in decimal.
Throws: NumberFormatException
if the string does not contain a parsable long.
o 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.

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.
o 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.

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

Overrides:
byteValue in class Number
o shortValue 
 public short shortValue()
Returns the value of this Long as a short.

Overrides:
shortValue in class Number
o intValue 
 public int intValue()
Returns the value of this Long as an int.

Returns:
the long value represented by this object is converted to type int and the result of the conversion is returned.
Overrides:
intValue in class Number
o longValue 
 public long longValue()
Returns the value of this Long as a long.

Returns:
the long value represented by this object.
Overrides:
longValue in class Number
o floatValue 
 public float floatValue()
Returns the value of this Long as a float.

Returns:
the long value represented by this object is converted to type float and the result of the conversion is returned.
Overrides:
floatValue in class Number
o doubleValue 
 public double doubleValue()
Returns the value of this Long as a double.

Returns:
the long value represented by this object that is converted to type double and the result of the conversion is returned.
Overrides:
doubleValue in class Number
o toString 
 public String toString()
Returns a String object representing this Long's value.

Returns:
a string representation of this object in base 10.
Overrides:
toString in class Object
o hashCode 
 public int hashCode()
Computes a hashcode for this Long.

Returns:
a hash code value for this object.
Overrides:
hashCode in class Object
o 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.

Parameters:
obj - the object to compare with.
Returns:
true if the objects are the same; false otherwise.
Overrides:
equals in class Object
o 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 getProperty and , a method defined by the System class. 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.

Parameters:
nm - property name.
Returns:
the Long value of the property.
See Also:
getProperty, getProperty
o 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 getProperty and , a method defined by the System class. 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.

Parameters:
nm - property name.
val - default value.
Returns:
the Long value of the property.
See Also:
getProperty, getProperty
o 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 getProperty and , a method defined by the System class. The string value of this property is then interpreted as a long value and a Long object representing this value is returned.

If the property value begins with "0x" or "#", not followed by a minus sign, the rest of it is parsed as a hexadecimal integer exactly as for the method Long.valueOf with radix 16.

If the property value begins with "0", then it is parsed as an octal integer exactly as for the method Long.valueOf with radix 8.

Otherwise the property value is parsed as a decimal integer exactly as for the method Long.valueOf with radix 10.

Note that, in every case, neither L nor l is permitted to appear at the end of the string.

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 - the property name.
val - the default Long value.
Returns:
the long value of the property.
See Also:
valueOf, getProperty, getProperty 
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