Java基础运算与println语句中的运算规则解析,-优快云博客

本文通过示例展示了Java中println语句中的运算规则，包括数字加号的含义，以及基础运算如加减乘除和取模的使用。着重解释了数字和字符串拼接的区别以及运算顺序。

-尝试：

首先，对println语句中的运算规则进行如下尝试性计算：

package com.pancake;

public class Test {

    public static void main(String args[]){
        int a=3,b=5;

        //test1:测试“+”作用
        System.out.println("a=");
        System.out.println("a="+a);

        //test2:测试""作用
        System.out.println("");

        //test3:组合测试
        System.out.println(a+b);
        System.out.println("a+b");
        System.out.println(a+b+""+a);
        System.out.println(a+b+""+a+b);
        System.out.println(a+b+"k"+a+b);
        System.out.println(a+b+""+a+b);
        System.out.println(a+b+""+a*b);

    }//of main
}//of class Test

得到如下结果：

a=
a=3

8
a+b
83
835
8k35
835
815

显然，在遇到变量/字符/字符串前，数字之间的加号即为两数相加；遇到后，加号即变成拼接。并且，仅加号会变成拼接，而+，/，%等不会变成拼接。同时应该注意Java运算先后顺序，即要优先选括号里面的内容。

-编写基础运算：

package com.pancake;

public class BasicOperations {

    public static void main(String args[]){
        int tempFirstInt,tempSecondInt,tempResultInt;
        double tempFirstDouble,tempSecondDouble,tempResultDouble;

        tempFirstInt = 15;
        tempSecondInt = 4;

        tempFirstDouble = 1.2;
        tempSecondDouble = 3.5;

        //Addition
        tempResultInt = tempFirstInt + tempSecondInt;
        tempResultDouble = tempFirstDouble + tempSecondDouble;

        System.out.println("" + tempFirstInt + " + " + tempSecondInt + " = " + tempResultInt);
        System.out.println("" + tempFirstDouble + " + " + tempSecondDouble + " = " + tempResultDouble);

        //Subtraction
        tempResultInt = tempFirstInt - tempSecondInt;
        tempResultDouble = tempFirstDouble - tempSecondDouble;

        System.out.println("" + tempFirstInt + " - " + tempSecondInt + " = " + tempResultInt);
        System.out.println("" + tempFirstDouble + " - " + tempSecondDouble + " = " + tempResultDouble);

        //Multiplication
        tempResultInt = tempFirstInt / tempSecondInt;
        tempResultDouble = tempFirstDouble / tempSecondDouble;

        System.out.println("" + tempFirstInt + " / " + tempSecondInt + " = " + tempResultInt);
        System.out.println("" + tempFirstDouble + " / " + tempSecondDouble + " = " + tempResultDouble);

        //Modulus
        tempResultInt = tempFirstInt % tempSecondInt;

        System.out.println("" + tempFirstInt + " % " + tempSecondInt + " = " + tempResultInt);
    }//of main
}//of class BasicOperations

最终输出：