java变量

Posted 2021-02-03 150643com

class Demo
{
    public static void main(String[] args)
    {
        byte a = 3;
        System.out.print(a);
    }
}

byte -128到 +128

class Demo
{
    public static void main(String[] args)
    {
        byte a = 300;//这里会报错
        System.out.print(a);
    }
}

超出+128 损失精度

C:UsersadminDesktopd1>javac 123.java
123.java:5: 错误: 不兼容的类型: 从int转换到byte可能会有损失
                byte a = 300;
                         ^
1 个错误

class Demo
{
    public static void main(String[] args)
    {
        byte a = 30;
        short b = 4000; 
        int x = 12;
        long l = 12345678;


        
/*
        float f = 2.3;
        C:UsersadminDesktopd1>javac 123.java
123.java:11: 错误: 不兼容的类型: 从double转换到float可能会有损失
                float f = 2.3;
                          ^
1 个错误
*/
        float f = 2.3f;
        double d = 3.4;

        char ch = ‘a‘;

        boolean bl = true;
        bl = false;
        System.out.print(bl);
    }
}