说明：Byte 类的实现，有一部分方法是借助于 Integer 类的实现.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package jdk.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}.
*
* @author Nakul Saraiya
* @author Joseph D. Darcy
* @see java.lang.Number
* @since JDK1.1
*/
public final class Byte extends Number implements Comparable<Byte> {
/**
* byte 最小值的常量{@code byte}可以具有-2 ^ 7.
* Java 中用补码表示二进制数, 补码最高位表示符号位，0 表示正数，1 表示负数.
* 正数补码为其本身; 负数补码为其各位取反加1；
*/
public static final byte MIN_VALUE = -128;
/**
* byte 最大值为 2 ^ 7 -1.
*/
public static final byte MAX_VALUE = 127;
/**
* The {@code Class} instance representing the primitive type
* {@code byte}.
*/
public static final Class<Byte> TYPE = (Class<Byte>) Class.getPrimitiveClass("byte");
/**
* 返回表示指定的{@code byte}的新{@code String}对象. 假设基数为10.
*
* @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);
}
/**
* Byte对象的缓存类
*/
private static class ByteCache {
private ByteCache(){}
/**
* 缓存数组
*/
static final Byte cache[] = new Byte[-(-128) + 127 + 1];
static {
// 缓存初始化，范围是-128到127
for(int i = 0; i < cache.length; i++)
cache[i] = new Byte((byte)(i - 128));
}
}
/**
* 封装基础byte到Byte对象，不过就是从缓存数组中取出对应的值.
* 说明：这里的这种处理方法和 Boolean 中的 valueOf 方法的处理方式类似，都是先定义
* 好了取值范围，然后直接返回定义好的值的引用即可.
*
* @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];
}
/**
* 将字符串按照指定的基数 radix 解析成 byte.
*
* @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;
}
/**
* 将字符串 s 解析成 基数为 10 进制的 byte.
*
* @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);
}
/**
* 将字符串按照指定的基数 radix 解析成 Byte.
*
* @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));
}
/**
* 将字符串 s 解析成 基数为 10 进制的 Byte.
*
* @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);
}
/**
* 将{@code String}解码为{@code Byte}. 接受以下语法给出的十进制，十六进制和八进制数：
* 0x|0X|#|0
*
* @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;
/**
* 构造一个新分配的{@code Byte}对象，该对象表示指定的{@code byte}值.
*
* @param value the value to be represented by the
* {@code Byte}.
*/
public Byte(byte value) {
this.value = value;
}
/**
* 构造一个新分配的{@code Byte}对象，该对象表示{@code String}参数指示的{@code byte}值.
* 字符串将以{@code parseByte}方法用于基数10的方式转换为{@code byte}值.
*
* @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}.
*/
public short shortValue() {
return (short)value;
}
/**
* Returns the value of this {@code Byte} as an
* {@code int}.
*/
public int intValue() {
return (int)value;
}
/**
* Returns the value of this {@code Byte} as a
* {@code long}.
*/
public long longValue() {
return (long)value;
}
/**
* Returns the value of this {@code Byte} as a
* {@code float}.
*/
public float floatValue() {
return (float)value;
}
/**
* Returns the value of this {@code Byte} as a
* {@code double}.
*/
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}
*/
public int hashCode() {
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);
}
/**
* 以数字方式比较两个{@code byte}值.
*
* <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;
}
/**
* 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;
/** use serialVersionUID from JDK 1.1. for interoperability */
private static final long serialVersionUID = -7183698231559129828L;
}