Java 变量、数据类型

public class Variable {
    static final int YEAR = 365;
    // 常量使用 final 修饰, 不可修改，类似C++的 const

    static int day = 0;
    // 成员变量

    public static void main(String[] args)
    {
        System.out.println("2年有：" + 2*YEAR + "天");
        for(int i = 0; i < 3; ++i)
        {
            System.out.println(day++);
        }
    }
}

2年有：730天
0
1
2

byte a1 = Byte.MAX_VALUE, a2 = Byte.MIN_VALUE;
System.out.println(a1 + " " + a2);// 127 -128

short b1 = Short.MAX_VALUE, b2 = Short.MIN_VALUE;
System.out.println(b1 + " " + b2);// 32767 -32768

int c1 = Integer.MAX_VALUE, c2 = Integer.MIN_VALUE;
System.out.println(c1 + " " + c2); // 2147483647 -2147483648

long d1 = Long.MAX_VALUE, d2 = Long.MIN_VALUE;
System.out.println(d1 + " " + d2);
// 9223372036854775807 -9223372036854775808

float num = 3.0F;// 或者 3.0f
System.out.println(num*num);// 9.0

double num2 = 5.2e52d;//没有d或者D也行
double num3 = 1.1E51;
System.out.println(num2+num3);// 5.31E52

char ch1 = 97;
char ch2 = 'a';
System.out.println(ch1);// a
System.out.println(ch2);// a

boolean flag = false;
if(flag)
    System.out.println("flag is " + flag);
else
    System.out.println("flag is " + flag);
    // flag is false

int x = 100;
double y = 3.0;
System.out.println(x/y);// 33.333333333333336
// 类型转换

// 强制转换 (type) var
int z = 3;
System.out.println(x/z); // 33
System.out.println((float)x/z);// 33.333332
System.out.println(x/(float)z);// 33.333332
System.out.println((float)x/(float)z);// 33.333332

int A = (int)1e301;
System.out.println(A);// 2147483647