03. 算术运算符

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FengXueke 10月 18, 2022
post03

算术运算符

  1. 基本算术运算符用法
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//: ShortCircuit.java
// Demonstrates short-circuiting behavior
// with logical operators.
package com.isflee.c03_1_3_math_ops;

import java.util.Random;

public class MathOps {


    // Create a shorthand to save typing:
    static void prt(String s) {
        System.out.println(s);
    }
    // shorthand to print a string and an int:
    static void pInt(String s, int i) {
        prt(s + " = " + i);
    }
    // shorthand to print a string and a float:
    static void pFlt(String s, float f) {
        prt(s + " = " + f);
    }
    public static void main(String[] args) {
        // Create a random number generator,
        // seeds with current time by default:
        Random rand = new Random();
        int i, j, k;
        // '%' limits maximum value to 99:
        j = rand.nextInt() % 100;
        k = rand.nextInt() % 100;
        pInt("j",j); pInt("k",k);
        i = j + k; pInt("j + k", i);
        i = j - k; pInt("j - k", i);
        i = k / j; pInt("k / j", i);
        i = k * j; pInt("k * j", i);
        i = k % j; pInt("k % j", i);
        j %= k; pInt("j %= k", j);
        // Floating-point number tests:
        float u,v,w;
        // applies to doubles, too
        v = rand.nextFloat();
        w = rand.nextFloat();
        pFlt("v", v); pFlt("w", w);
        u = v + w; pFlt("v + w", u);
        u = v - w; pFlt("v - w", u);
        u = v * w; pFlt("v * w", u);
        u = v / w; pFlt("v / w", u);
        // the following also works for
        // char, byte, short, int, // and double:
        u += v;
        pFlt("u += v", u);
        u -= v;
        pFlt("u -= v", u);
        u *= v;
        pFlt("u *= v", u);
        u /= v;
        pFlt("u /= v", u);
    }
} ///:~

  1. 自动递增和递减

++ 和 --
符号在前先加减, 符号在后后加减

  • 示例
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//: AutoInc.java
// Demonstrates the ++ and -- operators
package com.isflee.c03_1_4_auto_inc;

public class AutoInc {

    //符号在前先加减， 符号在后后加减
    public static void main(String[] args) {
        int i = 1;
        prt("i : " + i);
        prt("++i : " + ++i); // Pre-increment
        prt("i++ : " + i++); // Post-increment
        prt("i : " + i);
        prt("--i : " + --i); // Pre-decrement
        prt("i-- : " + i--); // Post-decrement
        prt("i : " + i);
    }
    static void prt(String s) {
        System.out.println(s);
    }
} ///:~

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输出结果
i:1
++i : 2 
i++ : 2 
i:3 
--i : 2 
i-- : 2 
i:1