Question

这是一个简单的计算器，我需要使用基本命令才能运行。这个项目的目标是编写异常（非常简单），但是，对于我的生活，我无法弄清楚这一点。我到处寻找。

无论是if / else语句还是Switch / Case语句，都会跳过thrid语句。当用户输入＆＃34; m＆＃34;它应该将计算的值保存到占位符变量中以便能够被调用（同样，超级简单）。我在添加部分添加了一个默认的case语句，并将我的save方法添加到默认语句中，它完美地运行。每个其他命令（r用于调用，c用于清除，e用于退出）也很有效。 m for save完全没有.....

apply plugin: 'groovy'

repositories {
   maven {
             url repository_url
             credentials {
                 username = artifactory_user
                 password = artifactory_password
             }
         }
}

dependencies {
    compile(
        'com.oracle:ojdbc6:11.2.0.1.0',
        'javax.xml.bind:jsr173_api:1.0',
        'org.apache.directory:groovy-ldap:1.0',
        'org.codehaus.groovy:groovy-all:2.4.5',
        'weblogic:wlfullclient:10.3.6',
        'javax.jms:jms:1.1'
    )

    testCompile(
        'junit:junit:4.12',
        'org.spockframework:spock-core:1.0-groovy-2.4'
    )
}

sourceSets {
    unit {
        groovy {
            srcDir file('src/test/unit/groovy')
            exclude '**/integration/**'
        }
        resources {
            srcDir file('src/test/resources')
        }
        compileClasspath += sourceSets.main.output + sourceSets.test.output + configurations.testRuntime
        runtimeClasspath += sourceSets.main.output + sourceSets.test.output + configurations.testRuntime
    }

    integration {
        groovy {
            srcDir 'src/test/integration/groovy'
            exclude '**/unit/**'
        }
        resources {
            srcDir 'src/test/resources'
        }
        compileClasspath += sourceSets.main.output + sourceSets.test.output + configurations.testRuntime
        runtimeClasspath += sourceSets.main.output + sourceSets.test.output + configurations.testRuntime
        }
    }

configurations {
    unitCompile.extendsFrom testCompile
    unitRuntime.extendsFrom testRuntime

    integrationCompile.extendsFrom testCompile
    integrationRuntime.extendsFrom testRuntime
}

task unit(type: Test) {
    include '**/unit/**'
    testClassesDir = sourceSets.unit.output.classesDir
    classpath = sourceSets.unit.runtimeClasspath
}

task integration(type: Test) {
    include '**/integration/**'
    testClassesDir = sourceSets.integration.output.classesDir
    classpath = sourceSets.integration.runtimeClasspath
    outputs.upToDateWhen { false }
}

}

有问题的主要代码是：我知道其他人没有默认或中断声明。这个，我正在调试并试图找出m失败的原因。现在，如果你是他，它只是转到默认的case语句，但没有解决问题。

import java.util.Scanner;

public class Calculator {
public static Scanner input = new Scanner(System.in);
public static double placeHolder;

public static void clear() {
    System.out.println("Save has been deleted, Screen has been cleared.");
}

public static void end() {
    System.out.println("Program ended..");
    input.close();
    System.exit(0);
}

public static void save(double initValue) {
    System.out.println("Number saved!");
    placeHolder = initValue;
}

public static void recall() {
    if (placeHolder != 0){
        System.out.println("Memory Place Holder Set To: " + placeHolder);
    }
    else {
        System.out.println("There is no data saved.");
    }
}

public static void commands() {
    System.out.println("e = end | c = clear | m = save | r = recall | o = continue");
    String command = input.nextLine();
    if (command.equals("e")){
        end();
    }
    else if (command.equals("c")){
        clear();
    }
    else if (command.equals("r")){
        recall();
    }

}




public static void main(String[] args) {
    boolean loop = true;
    while (loop == true){
        commands();
        System.out.println("Please enter what you would like to do: (+,-,*,/,%)");
        String function = input.nextLine();
        System.out.println("Enter the first number to be calucalted (If dividing, this is the numerator):");
        double n1 = input.nextDouble();
        System.out.println("Enter the second number to be calucalted (If dividing, this is the denominator):");
        double n2 = input.nextDouble();

        //=======================
        // Addition
        //=======================
        if (function.equals("+")){
            double sum = n1+n2;
            System.out.println(n1+"+"+ n2 +" = " + sum);
            System.out.println("e = end | c = clear | m = save | r = recall");
            String command = input.nextLine();
            input.nextLine();
            switch (command){
            case "e":
                end();
                break;
            case "c":
                clear();
                break;
            case "m":
                save(sum);
                break;
            case "r":
                recall();
                break;
            default: 
                System.out.println("Default");
                save(sum);
                break;
            }

        }
        //=======================
        // Subtraction
        //=======================
        else if (function.equals("-")){
            double sum = n1-n2;
            System.out.println(n1 + "-" + n2 +" = " + sum);
            System.out.println("e = end | c = clear | m = save | r = recall");
            String command = input.nextLine();
            input.nextLine();
            switch (command){
            case "e":
                end();
            case "c":
                clear();
            case "m":
                save(sum);
            case "r":
                recall();
            }
        }
        //=======================
        // Multiplication
        //=======================
        else if (function.equals("*")){
            double sum = n1*n2;
            System.out.println(n1 + "*" + n2 +" = " + sum);
            System.out.println("e = end | c = clear | m = save | r = recall");
            String command = input.nextLine();
            input.nextLine();
            switch (command){
            case "e":
                end();
            case "c":
                clear();
            case "m":
                save(sum);
            case "r":
                recall();
            }
        }
        //=======================
        // Division
        //=======================
        else if (function.equals("/")){
            double sum = n1/n2;
            System.out.println(n1 + "/" + n2 +" = " + sum);
            System.out.println("e = end | c = clear | m = save | r = recall");
            String command = input.nextLine();
            input.nextLine();
            switch (command){
            case "e":
                end();
            case "c":
                clear();
            case "m":
                save(sum);
            case "r":
                recall();
            }
        }
        //=======================
        // Mod
        //=======================
        else if (function.equals("%")){
            double sum = n1%n2;
            System.out.println(n1 + "%" + n2 +" = " + sum);
            System.out.println("e = end | c = clear | m = save | r = recall");
            String command = input.nextLine();
            input.nextLine();
            switch (command){
            case "e":
                end();
            case "c":
                clear();
            case "m":
                save(sum);
            case "r":
                recall();
            }
        }
    }   

        //=======================
        // Dictate loop duration:
        //=======================
        System.out.println("Would you like to continue? (Y|N): ");
        String ans = input.nextLine();
        if (ans.equals("N") || ans.equals("n")){
            System.out.println("Closing Program");
            loop = false;
            end();
        }
    }

=============================================== ========================== 以下是在事后查看此帖子的人的修复：

 switch (command){
        case "e":
            end();
            break;
        case "c":
            clear();
            break;
        case "m":
            save(sum);
            break;
        case "r":
            recall();
            break;
        default: 
            System.out.println("Default");
            save(sum);
            break;

Answer 1

每input.nextDouble();后，您需要致电input.nextLine();消费新行，请参阅Scanner is skipping nextLine() after using next(), nextInt() or other nextFoo() methods
在每input.nextLine();

String command = input.nextLine();

Answer 2

nextDouble()不消耗新行。您可以通过解析整行来解决这个问题，然后使用Double.parseDouble()来获取此行中的double值

....
    System.out.println("Enter the first number to be"+ 
          "calculated (If dividing, this is the numerator):");

    double n1 = Double.parseDouble(input.nextLine());

    System.out.println("Enter the second number to be" + 
          "calculated (If dividing, this is the denominator):");

    double n2 = Double.parseDouble(input.nextLine());

    if (function.equals("+")) {
     double sum = n1 + n2;
     System.out.println(n1 + "+" + n2 + " = " + sum);
     System.out.println("e = end | c = clear | m = save | r = recall");
     String command = input.nextLine();

     switch (command) {
     case "e":
      end();
      break;
      case "c":
      clear();
      break;
     case "m":
      save(sum);
      break;
     case "r":
      recall();
      break;
     }
....

注意

您不必使用布尔变量检查while(loop == true)，您可以通过while(loop)进行检查。

Answer 3

选中此Complete code link

您需要照顾的事情很少。

进行良好的异常处理。
验证用户输入

我对您的代码所做的更改 -

清除placeHolder方法

clear()

使用input.next()代替input.nextLine()并删除额外的input.newLine()方法
将break语句添加到所有switch语句

您需要在代码中模块化很多东西。看看Best Coding练习

Answer 4

input.nextDouble()读取数字，但对行尾没有任何作用。所以当你稍后在代码中执行此操作时：

String command = input.nextLine();

它处理线的左端，而不是＆＃34; m＆＃34;你输入下一个。

要修复，请执行一些操作来处理输入的行尾，例如在调用nextDouble（）之后添加input.nextLine（）：

double n1 = input.nextDouble();
input.nextLine();
double n2 = input.nextDouble();
input.nextLine();

Java跳过第三种情况声明

4 个答案: