自加++（Java版本）

• 变量++ 先取值，后加1
• ++变量 先加1，后取值
• 先看一个小栗子，先取值故result是num初始的值，num的值是num自加一后的值

import java.util.Scanner;
public class HelloWorld {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("输入num: " );
        int num = sc.nextInt();
        int result = num++ ;
        System.out.println("此时num是：" + num);
        System.out.println("result is " + result);
    }
}

• 详细说明
  

import java.util.Scanner;
public class HelloWorld {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("输入num: " );
        int num = sc.nextInt();
        int result = num++ + num++ + num++ + num*2;
        System.out.println("此时num是：" + num);
        System.out.println("result is " + result);
    }
}

• num = num++；num的值取决于编译，假设num的值是1，先取值为1，再自加num = 2，但是赋值是赋先取出来的值1，所以num自加为2的结果被覆盖，最终为1

import java.util.Scanner;
public class HelloWorld {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("输入num: " );
        int num = sc.nextInt();
        num = num++;
        System.out.println("此时num是：" + num);
    }
}

• 自加与逻辑运算&&，&&只要前一个判断为假，后面判断便不进行，所以num不会自加，直接输出结果

import java.util.Scanner;
public class HelloWorld {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("输入num: " );
        int num = sc.nextInt();
        boolean result = num > 2 && num++%2 == 1;
        System.out.println("逻辑判断是：" + result);
        System.out.println("此时num是：" + num);
    }
}