查看“Java中的整型”的源代码

=== 怎样输出整型的二进制形式 ===
<syntaxhighlight lang="java">
public class Test {

    public static void main(String[] args) {

        System.out.printf("binary string of %d: %s\n", 7, Integer.toBinaryString(7));

        System.out.printf("binary string of %d: %s\n", -7, Integer.toBinaryString(-7));

    }

}
</syntaxhighlight><syntaxhighlight lang="console">
binary string of 7: 111
binary string of -7: 11111111111111111111111111111001
</syntaxhighlight>如果想要正数显示全 ，可以：<syntaxhighlight lang="java">
public class Test {

    public static void main(String[] args) {

        System.out.printf("binary string of %d: %s\n", 7, String.format("%32s", Integer.toBinaryString(7)).replace(' ', '0'));

        System.out.printf("binary string of %d: %s\n", -7, Integer.toBinaryString(-7));

    }

}
</syntaxhighlight><syntaxhighlight lang="console">
binary string of 7: 00000000000000000000000000000111
binary string of -7: 11111111111111111111111111111001
</syntaxhighlight>int 4个字节（byte），32位（bit），1个符号位（0-正，1-负），

==== 正数 ====
就是十进制转二进制，其余位（bit）为0；
{| class="wikitable"
!1
符号位
!2
!3
!4
!5
!6
!7
!8
!9
!10
!11
!12
!13
!14
!15
!16
!17
!18
!19
!20
!21
!22
!23
!24
!25
!26
!27
!28
!29
!30
2<sup>2</sup>
!31
2<sup>1</sup>
!32
2<sup>0</sup>
|-
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|1
|1
|1
|}
2<sup>2</sup>+2<sup>1</sup>+2<sup>0</sup>=4+2+1=7

==== 负数 ====
则是补码存储：

①十进制转为二进制得到：
{| class="wikitable"
!1
符号位
!2
!3
!4
!5
!6
!7
!8
!9
!10
!11
!12
!13
!14
!15
!16
!17
!18
!19
!20
!21
!22
!23
!24
!25
!26
!27
!28
!29
!30
2<sup>2</sup>
!31
2<sup>1</sup>
!32
2<sup>0</sup>
|-
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|0
|1
|1
|1
|}
②然后取反码，再得到：
{| class="wikitable"
!1
符号位
!2
!3
!4
!5
!6
!7
!8
!9
!10
!11
!12
!13
!14
!15
!16
!17
!18
!19
!20
!21
!22
!23
!24
!25
!26
!27
!28
!29
!30
2<sup>2</sup>
!31
2<sup>1</sup>
!32
2<sup>0</sup>
|-
|0
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|0
|0
|0
|}
③反码再+1，得到补码：
{| class="wikitable"
!1
符号位
!2
!3
!4
!5
!6
!7
!8
!9
!10
!11
!12
!13
!14
!15
!16
!17
!18
!19
!20
!21
!22
!23
!24
!25
!26
!27
!28
!29
!30
2<sup>2</sup>
!31
2<sup>1</sup>
!32
2<sup>0</sup>
|-
|0
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|0
|0
|1
|}
④最后，首位（bit）是符号，值为二进制的1，表示负数：
{| class="wikitable"
!1
符号位
!2
!3
!4
!5
!6
!7
!8
!9
!10
!11
!12
!13
!14
!15
!16
!17
!18
!19
!20
!21
!22
!23
!24
!25
!26
!27
!28
!29
!30
2<sup>2</sup>
!31
2<sup>1</sup>
!32
2<sup>0</sup>
|-
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|1
|0
|0
|1
|}


=== 怎么验证呢？ ===
java8中已经加入了在声明整型变量时对二进制形式字面量声明的支持：<syntaxhighlight lang="java">
public class Test1 {

    public static void main(String[] args) {

        int a = 0b00000000000000000000000000000111;
        int b = 0b11111111111111111111111111111001;
        System.out.printf("a=%d\n", a);
        System.out.printf("b=%d\n", b);

    }

}
</syntaxhighlight><syntaxhighlight lang="console">
a=7
b=-7
</syntaxhighlight>