/*
* Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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package java.lang;
/**
*
* The {@code Byte} class wraps a value of primitive type {@code byte}
* in an object. An object of type {@code Byte} contains a single
* field whose type is {@code byte}.
*
* <p>In addition, this class provides several methods for converting
* a {@code byte} to a {@code String} and a {@code String} to a {@code
* byte}, as well as other constants and methods useful when dealing
* with a {@code byte}.
*
* 和其他基本类大同小异
* @author Nakul Saraiya
* @author Joseph D. Darcy
* @see java.lang.Number
* @since JDK1.1
*
* My Note
* 基本上复用了Integer的所有方法，8 bit
*
*/
public final class Byte extends Number implements Comparable<Byte> {
/**
* A constant holding the minimum value a {@code byte} can
* have, -2<sup>7</sup>.
*/
public static final byte MIN_VALUE = -128;
/**
* A constant holding the maximum value a {@code byte} can
* have, 2<sup>7</sup>-1.
*/
public static final byte MAX_VALUE = 127;
/**
* The {@code Class} instance representing the primitive type
* {@code byte}.
*/
@SuppressWarnings("unchecked")
public static final Class<Byte> TYPE = (Class<Byte>) Class.getPrimitiveClass("byte");
/**
* Returns a new {@code String} object representing the
* specified {@code byte}. The radix is assumed to be 10.
* -128 ~ 127
* @param b the {@code byte} to be converted
* @return the string representation of the specified {@code byte}
* @see java.lang.Integer#toString(int)
*/
public static String toString(byte b) {
return Integer.toString((int)b, 10);
}
private static class ByteCache {
private ByteCache(){}
static final Byte cache[] = new Byte[-(-128) + 127 + 1];
static {
for(int i = 0; i < cache.length; i++)
cache[i] = new Byte((byte)(i - 128));
}
}
/**
* Returns a {@code Byte} instance representing the specified
* {@code byte} value.
* If a new {@code Byte} instance is not required, this method
* should generally be used in preference to the constructor
* {@link #Byte(byte)}, as this method is likely to yield
* significantly better space and time performance since
* all byte values are cached.
*
* @param b a byte value.
* @return a {@code Byte} instance representing {@code b}.
* @since 1.5
*/
public static Byte valueOf(byte b) {
final int offset = 128;
return ByteCache.cache[(int)b + offset];
}
/**
* Parses the string argument as a signed {@code byte} 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 {@link java.lang.Character#digit(char,
* int)} returns a nonnegative value) except that the first
* character may be an ASCII minus sign {@code '-'}
* ({@code '\u005Cu002D'}) to indicate a negative value or an
* ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
* indicate a positive value. The resulting {@code byte} value is
* returned.
*
* <p>An exception of type {@code NumberFormatException} is
* thrown if any of the following situations occurs:
* <ul>
* <li> The first argument is {@code null} or is a string of
* length zero.
*
* <li> The radix is either smaller than {@link
* java.lang.Character#MIN_RADIX} or larger than {@link
* java.lang.Character#MAX_RADIX}.
*
* <li> Any character of the string is not a digit of the
* specified radix, except that the first character may be a minus
* sign {@code '-'} ({@code '\u005Cu002D'}) or plus sign
* {@code '+'} ({@code '\u005Cu002B'}) provided that the
* string is longer than length 1.
*
* <li> The value represented by the string is not a value of type
* {@code byte}.
* </ul>
*
* @param s the {@code String} containing the
* {@code byte}
* representation to be parsed
* @param radix the radix to be used while parsing {@code s}
* @return the {@code byte} value represented by the string
* argument in the specified radix
* @throws NumberFormatException If the string does
* not contain a parsable {@code byte}.
*/
public static byte parseByte(String s, int radix)
throws NumberFormatException {
int i = Integer.parseInt(s, radix);
if (i < MIN_VALUE || i > MAX_VALUE)
throw new NumberFormatException(
"Value out of range. Value:\"" + s + "\" Radix:" + radix);
return (byte)i;
}
/**
* Parses the string argument as a signed decimal {@code
* byte}. The characters in the string must all be decimal digits,
* except that the first character may be an ASCII minus sign
* {@code '-'} ({@code '\u005Cu002D'}) to indicate a negative
* value or an ASCII plus sign {@code '+'}
* ({@code '\u005Cu002B'}) to indicate a positive value. The
* resulting {@code byte} value is returned, exactly as if the
* argument and the radix 10 were given as arguments to the {@link
* #parseByte(java.lang.String, int)} method.
*
* @param s a {@code String} containing the
* {@code byte} representation to be parsed
* @return the {@code byte} value represented by the
* argument in decimal
* @throws NumberFormatException if the string does not
* contain a parsable {@code byte}.
*/
public static byte parseByte(String s) throws NumberFormatException {
return parseByte(s, 10);
}
/**
* Returns a {@code Byte} object holding the value
* extracted from the specified {@code String} when parsed
* with the radix given by the second argument. The first argument
* is interpreted as representing a signed {@code byte} in
* the radix specified by the second argument, exactly as if the
* argument were given to the {@link #parseByte(java.lang.String,
* int)} method. The result is a {@code Byte} object that
* represents the {@code byte} value specified by the string.
*
* <p> In other words, this method returns a {@code Byte} object
* equal to the value of:
*
* <blockquote>
* {@code new Byte(Byte.parseByte(s, radix))}
* </blockquote>
*
* @param s the string to be parsed
* @param radix the radix to be used in interpreting {@code s}
* @return a {@code Byte} object holding the value
* represented by the string argument in the
* specified radix.
* @throws NumberFormatException If the {@code String} does
* not contain a parsable {@code byte}.
*/
public static Byte valueOf(String s, int radix)
throws NumberFormatException {
return valueOf(parseByte(s, radix));
}
/**
* Returns a {@code Byte} object holding the value
* given by the specified {@code String}. The argument is
* interpreted as representing a signed decimal {@code byte},
* exactly as if the argument were given to the {@link
* #parseByte(java.lang.String)} method. The result is a
* {@code Byte} object that represents the {@code byte}
* value specified by the string.
*
* <p> In other words, this method returns a {@code Byte} object
* equal to the value of:
*
* <blockquote>
* {@code new Byte(Byte.parseByte(s))}
* </blockquote>
*
* @param s the string to be parsed
* @return a {@code Byte} object holding the value
* represented by the string argument
* @throws NumberFormatException If the {@code String} does
* not contain a parsable {@code byte}.
*/
public static Byte valueOf(String s) throws NumberFormatException {
return valueOf(s, 10);
}
/**
* Decodes a {@code String} into a {@code Byte}.
* Accepts decimal, hexadecimal, and octal numbers given by
* the following grammar:
*
* <blockquote>
* <dl>
* <dt><i>DecodableString:</i>
* <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
* <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
* <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
* <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
* <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
*
* <dt><i>Sign:</i>
* <dd>{@code -}
* <dd>{@code +}
* </dl>
* </blockquote>
*
* <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
* are as defined in section 3.10.1 of
* <cite>The Java™ Language Specification</cite>,
* except that underscores are not accepted between digits.
*
* <p>The sequence of characters following an optional
* sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
* "{@code #}", or leading zero) is parsed as by the {@code
* Byte.parseByte} method with the indicated radix (10, 16, or 8).
* This sequence of characters must represent a positive value or
* a {@link NumberFormatException} will be thrown. The result is
* negated if first character of the specified {@code String} is
* the minus sign. No whitespace characters are permitted in the
* {@code String}.
*
* @param nm the {@code String} to decode.
* @return a {@code Byte} object holding the {@code byte}
* value represented by {@code nm}
* @throws NumberFormatException if the {@code String} does not
* contain a parsable {@code byte}.
* @see java.lang.Byte#parseByte(java.lang.String, int)
*/
public static Byte decode(String nm) throws NumberFormatException {
int i = Integer.decode(nm);
if (i < MIN_VALUE || i > MAX_VALUE)
throw new NumberFormatException(
"Value " + i + " out of range from input " + nm);
return valueOf((byte)i);
}
/**
* The value of the {@code Byte}.
*
* @serial
*/
private final byte value;
/**
* Constructs a newly allocated {@code Byte} object that
* represents the specified {@code byte} value.
*
* @param value the value to be represented by the
* {@code Byte}.
*/
public Byte(byte value) {
this.value = value;
}
/**
* Constructs a newly allocated {@code Byte} object that
* represents the {@code byte} value indicated by the
* {@code String} parameter. The string is converted to a
* {@code byte} value in exactly the manner used by the
* {@code parseByte} method for radix 10.
*
* @param s the {@code String} to be converted to a
* {@code Byte}
* @throws NumberFormatException If the {@code String}
* does not contain a parsable {@code byte}.
* @see java.lang.Byte#parseByte(java.lang.String, int)
*/
public Byte(String s) throws NumberFormatException {
this.value = parseByte(s, 10);
}
/**
* Returns the value of this {@code Byte} as a
* {@code byte}.
*/
public byte byteValue() {
return value;
}
/**
* Returns the value of this {@code Byte} as a {@code short} after
* a widening primitive conversion.
* @jls 5.1.2 Widening Primitive Conversions
*/
public short shortValue() {
return (short)value;
}
/**
* Returns the value of this {@code Byte} as an {@code int} after
* a widening primitive conversion.
* @jls 5.1.2 Widening Primitive Conversions
*/
public int intValue() {
return (int)value;
}
/**
* Returns the value of this {@code Byte} as a {@code long} after
* a widening primitive conversion.
* @jls 5.1.2 Widening Primitive Conversions
*/
public long longValue() {
return (long)value;
}
/**
* Returns the value of this {@code Byte} as a {@code float} after
* a widening primitive conversion.
* @jls 5.1.2 Widening Primitive Conversions
*/
public float floatValue() {
return (float)value;
}
/**
* Returns the value of this {@code Byte} as a {@code double}
* after a widening primitive conversion.
* @jls 5.1.2 Widening Primitive Conversions
*/
public double doubleValue() {
return (double)value;
}
/**
* Returns a {@code String} object representing this
* {@code Byte}'s value. The value is converted to signed
* decimal representation and returned as a string, exactly as if
* the {@code byte} value were given as an argument to the
* {@link java.lang.Byte#toString(byte)} method.
*
* @return a string representation of the value of this object in
* base 10.
*/
public String toString() {
return Integer.toString((int)value);
}
/**
* Returns a hash code for this {@code Byte}; equal to the result
* of invoking {@code intValue()}.
*
* @return a hash code value for this {@code Byte}
*/
@Override
public int hashCode() {
return Byte.hashCode(value);
}
/**
* Returns a hash code for a {@code byte} value; compatible with
* {@code Byte.hashCode()}.
*
* @param value the value to hash
* @return a hash code value for a {@code byte} value.
* @since 1.8
*/
public static int hashCode(byte value) {
return (int)value;
}
/**
* Compares this object to the specified object. The result is
* {@code true} if and only if the argument is not
* {@code null} and is a {@code Byte} object that
* contains the same {@code byte} value as this object.
*
* @param obj the object to compare with
* @return {@code true} if the objects are the same;
* {@code false} otherwise.
*/
public boolean equals(Object obj) {
if (obj instanceof Byte) {
return value == ((Byte)obj).byteValue();
}
return false;
}
/**
* Compares two {@code Byte} objects numerically.
*
* @param anotherByte the {@code Byte} to be compared.
* @return the value {@code 0} if this {@code Byte} is
* equal to the argument {@code Byte}; a value less than
* {@code 0} if this {@code Byte} is numerically less
* than the argument {@code Byte}; and a value greater than
* {@code 0} if this {@code Byte} is numerically
* greater than the argument {@code Byte} (signed
* comparison).
* @since 1.2
*/
public int compareTo(Byte anotherByte) {
return compare(this.value, anotherByte.value);
}
/**
* Compares two {@code byte} values numerically.
* The value returned is identical to what would be returned by:
* <pre>
* Byte.valueOf(x).compareTo(Byte.valueOf(y))
* </pre>
*
* @param x the first {@code byte} to compare
* @param y the second {@code byte} to compare
* @return the value {@code 0} if {@code x == y};
* a value less than {@code 0} if {@code x < y}; and
* a value greater than {@code 0} if {@code x > y}
* @since 1.7
*/
public static int compare(byte x, byte y) {
return x - y;
}
/**
* Converts the argument to an {@code int} by an unsigned
* conversion. In an unsigned conversion to an {@code int}, the
* high-order 24 bits of the {@code int} are zero and the
* low-order 8 bits are equal to the bits of the {@code byte} argument.
*
* Consequently, zero and positive {@code byte} values are mapped
* to a numerically equal {@code int} value and negative {@code
* byte} values are mapped to an {@code int} value equal to the
* input plus 2<sup>8</sup>.
*
* @param x the value to convert to an unsigned {@code int}
* @return the argument converted to {@code int} by an unsigned
* conversion
* @since 1.8
*/
public static int toUnsignedInt(byte x) {
return ((int) x) & 0xff;
}
/**
* Converts the argument to a {@code long} by an unsigned
* conversion. In an unsigned conversion to a {@code long}, the
* high-order 56 bits of the {@code long} are zero and the
* low-order 8 bits are equal to the bits of the {@code byte} argument.
*
* Consequently, zero and positive {@code byte} values are mapped
* to a numerically equal {@code long} value and negative {@code
* byte} values are mapped to a {@code long} value equal to the
* input plus 2<sup>8</sup>.
*
* @param x the value to convert to an unsigned {@code long}
* @return the argument converted to {@code long} by an unsigned
* conversion
* @since 1.8
*/
public static long toUnsignedLong(byte x) {
return ((long) x) & 0xffL;
}
/**
* The number of bits used to represent a {@code byte} value in two's
* complement binary form.
*
* @since 1.5
*/
public static final int SIZE = 8;
/**
* The number of bytes used to represent a {@code byte} value in two's
* complement binary form.
*
* @since 1.8
*/
public static final int BYTES = SIZE / Byte.SIZE;
/** use serialVersionUID from JDK 1.1. for interoperability */
private static final long serialVersionUID = -7183698231559129828L;
}
Byte
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