Demo01

package operator;

/**
 * @projectName: JAVA程式設計
 * @package: operator
 * @className: Demo01
 * @author: IT_Jay
 * @description: TODO
 * @date: 2021/11/17 18:54
 */
public class Demo01 {
    public static void main(String[] args) {
        //二元運算子
        //ctrl + D :複製當前行到下一行
        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 為整型
        System.out.println(a/(double)b);
    }
}
 

• ctrl + D :複製當前行到下一行
• "/"取整： a/b 10 / 20 = 0.5 , 整數部分為0

Demo02

package operator;

/**
 * @projectName: JAVA程式設計
 * @package: operator
 * @className: Demo02
 * @author: IT_Jay
 * @description: TODO
 * @date: 2021/11/17 18:59
 */
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));  //不可將Int型轉換(cast)為String型
    }
}
 

• short型、byte型運算結果預設為int型

• System.out.println((String) (c+d));  //不可將Int型轉換(cast)為String型
  

Demo03

package operator;

/**
 * @author IT_Jay
 * @date 2021/11/21 21:13
 */

public class Demo03 {
    public static void main(String[] args) {
        //關係運算符返回布林值   True    False

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

        //取餘  模運算
        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);
    }
}
 

• 關係運算符結果返回布林值 True || False
• “%” 取餘 模運算 c /a 21 / 10 =2......1