首先byte、short、int、long都是整数类型。
①:byte占一个字节,也就是8位,而且byte 是有符号整形 用二进制表示时候最高位为符号位 0代表正数 1代表负数。
max:01111111(十进制:2^8-1=127)
min:是11111111吗?答案不是的。8位总共能表示256个数。00000000表示0,那10000000表示?
要注意正数在计算机中是以原码形式存在的,负数在计算机中是以其补码形式存在的,那么一个负数的补码是怎么计算的呢?
就是负数的绝对值的原码转为二进制再按位取反后加1。
-128的绝对值128,128源码10000000 取反:01111111 加1:10000000 故-128计算机中的表示就是 1000 0000 了。
-2^7(-128)<byte<2^7-1(127)
jdk中
Byte.class中的源代码:
/**
* A constant holding the minimum value a <code>byte</code> can
* have, -2<sup>7</sup>.
*/
public static final byte MIN_VALUE = -128;
/**
* A constant holding the maximum value a <code>byte</code> can
* have, 2<sup>7</sup>-1.
*/
public static final byte MAX_VALUE = 127;
②同理:short占2位,int占4位,long占8位,都是有符号整型。
/**
* A constant holding the minimum value a <code>short</code> can
* have, -2<sup>15</sup>.
*/
public static final short MIN_VALUE = -32768;
/**
* A constant holding the maximum value a <code>short</code> can
* have, 2<sup>15</sup>-1.
*/
public static final short MAX_VALUE = 32767;
* A constant holding the minimum value a <code>short</code> can
* have, -2<sup>15</sup>.
*/
public static final short MIN_VALUE = -32768;
/**
* A constant holding the maximum value a <code>short</code> can
* have, 2<sup>15</sup>-1.
*/
public static final short MAX_VALUE = 32767;
-2^15(-32768)<byte<2^15-1(32767)
/**
* A constant holding the minimum value an <code>int</code> can
* have, -2<sup>31</sup>.
*/
public static final int MIN_VALUE = 0x80000000;
/**
* A constant holding the maximum value an <code>int</code> can
* have, 2<sup>31</sup>-1.
*/
public static final int MAX_VALUE = 0x7fffffff;
* A constant holding the minimum value an <code>int</code> can
* have, -2<sup>31</sup>.
*/
public static final int MIN_VALUE = 0x80000000;
/**
* A constant holding the maximum value an <code>int</code> can
* have, 2<sup>31</sup>-1.
*/
public static final int MAX_VALUE = 0x7fffffff;
-2^31(-2147483648)<byte<2^31-1(2147483647)
/**
* A constant holding the minimum value a <code>long</code> can
* have, -2<sup>63</sup>.
*/
public static final long MIN_VALUE = 0x8000000000000000L;
/**
* A constant holding the maximum value a <code>long</code> can
* have, 2<sup>63</sup>-1.
*/
public static final long MAX_VALUE = 0x7fffffffffffffffL;
* A constant holding the minimum value a <code>long</code> can
* have, -2<sup>63</sup>.
*/
public static final long MIN_VALUE = 0x8000000000000000L;
/**
* A constant holding the maximum value a <code>long</code> can
* have, 2<sup>63</sup>-1.
*/
public static final long MAX_VALUE = 0x7fffffffffffffffL;
-2^63<byte<2^63-1
char作为16位无符号整形
其范围为 0 —— 2^15,float占4位,double占8位。