Java - 使用变量获取计算的答案答案

【问题标题】：Java - Getting the answer to a calculation using variablesJava - 使用变量获取计算的答案
【发布时间】：2015-03-29 10:57:45
【问题描述】：

我如何返回计算的答案，其中使用的两个数字和运算符存储在变量中（来自用户的输入）。

我正在创建一个简单的计算器并尝试将答案输出到 "Number" "Operator" "Number2"，这可以是任何取决于用户输入的内容。

int Number;
int Number2;
int Operator;
String OperatorString;

do 
{
    System.out.println("Enter a number");
    Number = UserInputScanner.nextInt();

    System.out.println("1. + \n");
    System.out.println("2. - \n");
    System.out.println("3. * \n");
    System.out.println("4. / \n");

    Operator = UserInputScanner.nextInt(); 

       switch (Operator) {
        case 1:  OperatorString = "+";          
                 break;
        case 2:  OperatorString = "-";
                 break;
        case 3:  OperatorString = "*";
                 break;
        case 4:  OperatorString = "/";
                 break;
        default: OperatorString = "Invalid Operator";
                 break;
    }
    System.out.println(OperatorString);

    System.out.println("Enter another number");
    Number2 = UserInputScanner.nextInt();       

    Answer = "Number" + "OperatorString" + "Number2";
    System.out.println(Number + OperatorString + Number2 + "=" + Answer);

输入这些数字和运算符时的输出返回“5+5=5+5”，而我试图返回“5+5=10”。

【问题讨论】：

您只是在答案Answer = "Number" + "OperatorString" + "Number2"; 中连接字符串，这不会给您想要的答案

标签： java variables calculator

【解决方案1】：

Java 没有提供使用运算符评估 String 表达式以生成结果值的内置方法，因此您需要另一个开关来计算 Answer：

switch (Operator) {
    case 1:  Answer = Number + Number2;
             break;
    case 2:  Answer = Number - Number2;
             break;
    case 3:  Answer = Number * Number2;
             break;
    case 4:  Answer = Number / Number2;
             break;
    default: Answer = 0;
             break;
}

开关的结构与读取第二个数字之前的结构相同，因此如果将Number2的读取移动到开关之前，则可以将两者结合起来。

【讨论】：

【解决方案2】：

在 Switch 块本身中计算答案

int Number;
int Number2;
int Operator;
String OperatorString;

do 
{
System.out.println("Enter a number");
Number = UserInputScanner.nextInt();

System.out.println("1. + \n");
System.out.println("2. - \n");
System.out.println("3. * \n");
System.out.println("4. / \n");

Operator = UserInputScanner.nextInt(); 
System.out.println("Enter another number");
Number2 = UserInputScanner.nextInt(); 
   switch (Operator) {
    case 1:  OperatorString = "+"; 
             Answer = Number + Number2;
             break;
    case 2:  OperatorString = "-";
             Answer = Number - Number2;
             break;
    case 3:  OperatorString = "*";
             Answer = Number * Number2;
             break;
    case 4:  OperatorString = "/";
             Answer = Number / Number2;
             break;
    default: OperatorString = "Invalid Operator";
             break;
}
System.out.println(OperatorString);




System.out.println(Number + OperatorString + Number2 + "=" + Answer);

【讨论】：