错误：二元运算符“-”的操作数类型错误答案

【问题标题】：error: bad operand types for binary operator '-'错误：二元运算符“-”的操作数类型错误
【发布时间】：2015-08-29 10:34:17
【问题描述】：

这是我的源代码：

/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
public static void main (String[] args) throws java.lang.Exception
{
    System.out.println( "Integer.MAX_VALUE = " +   Integer.MAX_VALUE );
    System.out.println( "Integer.MAX_VALUE + 1 = " +   (Integer.MAX_VALUE + 1) );
    System.out.println( "Integer.MAX_VALUE * 2 = " +  ( Integer.MAX_VALUE * 2) );
    System.out.println( "Integer.MAX_VALUE * 5 = " +  ( Integer.MAX_VALUE * 5) );
    System.out.println( "Integer.MAX_VALUE * 10 = " + (  Integer.MAX_VALUE * 10) );
    System.out.println( "Integer.MAX_VALUE = " +   Integer.MAX_VALUE );
    System.out.println( "Integer.MIN_VALUE - 1 = " +   (Integer.MIN_VALUE - 1) );
    System.out.println( "Integer.MIN_VALUE * 2 = " +  ( Integer.MIN_VALUE * 2) );
    System.out.println( "Integer.MIN_VALUE * 5 = " +  ( Integer.MIN_VALUE * 5) );
    System.out.println( "Integer.MIN_VALUE * 10 = " + (  Integer.MIN_VALUE * 10) );
    //Part 2
    System.out.println( "Integer.MAX_VALUE + 1.0 = " +   (Integer.MAX_VALUE + 1.0) );
    System.out.println( "Integer.MAX_VALUE * 2.0 = " +  ( Integer.MAX_VALUE * 2.0) );
    System.out.println( "Integer.MAX_VALUE * 5.0 = " +  ( Integer.MAX_VALUE * 5.0) );
    System.out.println( "Integer.MAX_VALUE * 10.0 = " + (  Integer.MAX_VALUE * 10.0) );
    System.out.println( "Integer.MIN_VALUE - 1.0 = " +   (Integer.MIN_VALUE - 1.0) );
    System.out.println( "Integer.MIN_VALUE * 2.0 = " +  ( Integer.MIN_VALUE * 2.0) );
    System.out.println( "Integer.MIN_VALUE * 5.0 = " +  ( Integer.MIN_VALUE * 5.0) );
    System.out.println( "Integer.MIN_VALUE * 10.0 = " + (  Integer.MIN_VALUE * 10.0) );
    //Part 3
    int a, b;
    a = 1;
    b = 2;
    System.out.println( "The ints a, b are " + a + ", " + b );
    System.out.println( "a + b is " + a + b );
    System.out.println( "a - b is " + a - b );
    System.out.println( "a * b is " + a * b );
    System.out.println( "a / b is " + a / b );
    //Part 4
    double aD, bD;
    aD = 1.0;
    bD = 2.0;
    System.out.println( "The doubles aD, bD are " + aD + ", " + bD  );
    System.out.println( "aD + bD is " + aD + bD );
    System.out.println( "aD - bD is "  + aD - bD );
    System.out.println( "aD * bD is " + aD * bD );
    System.out.println( "aD / bD is " + aD / bD );
}
}

这是我的错误：

Compilation error   time: 0.1 memory: 320512 signal:0
Main.java:37: error: bad operand types for binary operator '-'
    System.out.println( "a - b is " + a - b );
                                        ^
 first type:  String
 second type: int
Main.java:46: error: bad operand types for binary operator '-'
    System.out.println( "aD - bD is "  +aD - bD );
                                           ^
first type:  String
second type: double
2 errors

我是 Java 新手，但我仍在研究算术。我以为我做得很好，但我不明白出了什么问题。这很可能是一个真正的菜鸟错误，但你能告诉我我做错了什么吗？

【问题讨论】：

标签： java math

【解决方案1】：

"a - b is " + (a) - (b)`

意思是：

("a - b is " + (a)) - (b)

。左边（("a - b is " + (a))）是一个字符串，不能从字符串中减去。

你需要使用括号：

"a - b is " + (a - b)

【讨论】：

谢谢！我只是把脸拍得太厉害了。

【解决方案2】：

+ 和 - 被视为字符串操作，其中表达式从左到右进行计算。为了避免这种情况标记，减法具有高优先级，当您用 () 包围时会发生这种情况

    System.out.println( "a - b is " + (a - b) );

现在由于优先级，括号(a-b) 内的表达式首先求值，然后是从左到右的整个表达式。

【讨论】：