Java基础

package operator;


public class Demo01 {
    public static void main(String[] args) {
        //二元运算符
        //ctrl + D :复制当前行到下一行
        int a = 10;
        int b = 20;
        int c = 30;
        int d = 40;

        System.out.println(a+b);
        System.out.println(a-b);
        System.out.println(a*b);
        System.out.println(a/b);     //int 为整型
        System.out.println(a/(double)b);
    }
}

• ctrl + D :复制当前行到下一行
• "/"取整： a/b 10 / 20 = 0.5 , 整数部分为0

package operator;


public class Demo02 {

    public static void main(String[] args) {

    long a = 12341414141151454L;
    int b = 123;
    short c = 10;
    byte d = 8;

        System.out.println(a+b+c+d);   //Long
        System.out.println(b+c+d);      //Int
        System.out.println(c+d);        //Int
        System.out.println((double) c+d);//Double
        //System.out.println((String) (c+d));  //不可将Int型转换(cast)为String型
    }
}

• short型、byte型运算结果默认为int型

• System.out.println((String) (c+d));  //不可将Int型转换(cast)为String型
  

package operator;



public class Demo03 {
    public static void main(String[] args) {
        //关系运算符返回布尔值   True    False

        int a = 10;
        int b = 20;
        int c = 21;

        //取余  模运算
        System.out.println(c%a);            //c /a   21 / 10 =2......1

        System.out.println(a > b);
        System.out.println(a < b);
        System.out.println(a == b);
        System.out.println(a != b);
    }
}

• 关系运算符结果返回布尔值 True || False
• “%” 取余 模运算 c /a 21 / 10 =2…1