2020-06-26【运算符】

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package operator;

/**
 * 算术运算符
 */
public class OperatorDemo1 {
    public static void main(String[] args) {
        //定义两个变量
        int a = 6;
        int b = 4;

        System.out.println(a + b);
        System.out.println(a - b);
        System.out.println(a * b);
        System.out.println(a / b);
        System.out.println(a % b);
        //除法得到的是商，取余得到是余数

        //整数相除只能得到整数，要想得到小数，必须有浮点数的参数
        System.out.println(6.0 / 4);
    }
}

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package operator;

/**
 * 字符的"+"操作
 */
public class OperatorDemo2 {
    public static void main(String[] args) {
        //定义两个变量
        int i = 10;
        char c = 'A'; //'A'的值是65
        c = 'a'; //'a'的值是97
        c = '0'; //'0'的值是48
        System.out.println(i + c);

        //char ch = i + c;
        //char类型会被自动提升为int类型
        int j = i + c;
        System.out.println(j);

        //int k = 10 + 13.14;
        double d = 10 + 13.14;
    }
}

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package operator;

/**
 * 字符串的"+"操作
 */
public class OperatorDemo3 {
    public static void main(String[] args) {
        System.out.println("hello" + "World"); //helloWorld
        System.out.println("hello" + 626); //hello626
        System.out.println(626 + "day"); //626day

        System.out.println("hello" + 6 + 26); //hello626
        System.out.println(2019 + 1 + "年"); //2020年
    }
}

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package operator;

/**
 * 赋值运算符
 */
public class OperatorDemo4 {
    public static void main(String[] args) {
        //把10赋值给int类型的变量i
        int i = 10;
        System.out.println("i:" + i);

        // += 把左边和右边的数据做加法操作，结果赋值给左边
        i += 20;
        //i = i + 20;
        System.out.println("i:" + i);

        //注意：扩展的赋值运算符底层隐含了强制类型转换
        short s = 10;
        s += 20;
        //s = (short)(s + 20)
        System.out.println("s:" + s);
    }
}

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package operator;

/**
 * 自增自减运算符
 */
public class OperatorDemo5 {
    public static void main(String[] args) {
        //定义变量
        int i = 10;
        System.out.println("i:" + i); //10

        //单独使用
        //i++
        //++i
        //System.out.println("i:" + i);

        //参与操作使用
        //int j = i++;
        int j = ++i;
        System.out.println("i:" + i); //30
        System.out.println("j:" + j); //30
    }
}

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