Short是基本数据类型short的包装类。
1)声明部:
public final class Short extends Number implements Comparable<Short>
extends Number,override methods:
public abstract int intValue(); public abstract float floatValue(); public abstract long longValue(); public abstract double doubleValue(); public byte byteValue() { return (byte)intValue(); } public short shortValue() { return (short)intValue(); }
implements Comparable<Short> :
public int compareTo(Short anotherShort) { return compare(this.value, anotherShort.value); }
public static int compare(short x, short y) { return x - y; }
2)私有静态内部类
private static class ShortCache { private ShortCache(){} static final Short cache[] = new Short[-(-128) + 127 + 1]; static { for(int i = 0; i < cache.length; i++) cache[i] = new Short((short)(i - 128)); } }
Short类加载的时候,加载该内部类,内部类静态模块代码执行,初始化缓存对象数组。
3)Short初始化方法:
通过构造函数初始化,构造函数如下:
//构造函数方法重载 public Short(String s) throws NumberFormatException { this.value = parseShort(s, 10); } //构造函数方法重载 public Short(short value) { this.value = value; }
通过调用转换的方法,该系列方法如下:
public static short parseShort(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 (short)i; } public static short parseShort(String s) throws NumberFormatException { return parseShort(s, 10); } public static Short valueOf(String s, int radix) throws NumberFormatException { return valueOf(parseShort(s, radix)); } public static Short valueOf(String s) throws NumberFormatException { return valueOf(s, 10); } public static Short valueOf(short s) { final int offset = 128; int sAsInt = s; if (sAsInt >= -128 && sAsInt <= 127) { // must cache return ShortCache.cache[sAsInt + offset]; } return new Short(s); }
观察代码之间的调用关系。第一个方法返回short类型,第五个方法通过取缓存获得Short对象。
初始化例子:
short s_1 = 1; String str_1 = "1"; Short s1 = new Short(str_1); Short s2 = new Short(s_1); Short s3 = s_1; Short s4 = Short.parseShort(str_1); Short s5 = Short.valueOf(str_1); s1 == s2;//fasle s1 == s3;//fasle s2 == s3;//fasle s4 == s3;//true s5 == s3;//true
结论:同Byte.class分析,short类型自动装箱会去获取缓存的对象(-128~127);使用构造函数初始化new,是一个新的对象,不从缓存里去获取对象。
4)其他方法
//解码,将short范围内的二进制,八进制,十六进制转换为十进制 public static Short 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((short)i); } public static String toString(short s) { return Integer.toString((int)s, 10); } public String toString() { return Integer.toString((int)value); } @Override public int hashCode() { return Short.hashCode(value); } public static int hashCode(short value) { return (int)value; } public boolean equals(Object obj) { if (obj instanceof Short) { return value == ((Short)obj).shortValue(); } return false; } public static int toUnsignedInt(short x) { return ((int) x) & 0xffff; } public static long toUnsignedLong(short x) { return ((long) x) & 0xffffL; } //Returns the value obtained by reversing the order of the bytes in the two's //complement representation of the specified {@code short} value. public static short reverseBytes(short i) { return (short) (((i & 0xFF00) >> 8) | (i << 8)); }
e.g:
short s_1 = 1; short s_2 = -1; String str_2 = "0x21"; Short s6 = Short.decode(str_2);//33 Out.println(s6.toString());//33 Out.println(Short.toString(s6.shortValue()));//33 Out.println(s6.hashCode());//33 Out.println(Short.toUnsignedInt(s_1));//1 Out.println(Short.toUnsignedInt(s_2));//65535 Out.println(Short.toUnsignedLong(s_1));//1 Out.println(Short.toUnsignedLong(s_2));//65535 Out.println(s4.equals(s1));//true //高位低位反转 正数 Short s7 = 2; Short s8 = Short.reverseBytes(s7); Out.println(s8);//512 //负数 short s_3 = (short)-0B000000000000011;//符号位直接使用符号替代,声明使用原码,运算时候使用补码,根据运算结果得出补码,再转为原码 short s_4 = (short)-0B000001000000001; Out.println(s_4 == Short.reverseBytes(s_3));//true
5)属性:
Out.println("MAX:" + Short.MAX_VALUE); Out.println("MIN:" + Short.MIN_VALUE); Out.println("BYTES:" + Short.BYTES); Out.println("bit size:" + Short.SIZE); Out.println("primitive type:" + Short.TYPE); MAX:32767 MIN:-32768 BYTES:2 bit size:16 primitive type:short