标签：ble 源码分析 AC pareto instance object exce returns 进制
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
标签：ble 源码分析 AC pareto instance object exce returns 进制
原文地址：https://www.cnblogs.com/knsbyoo/p/9032471.html
