以前的输入被较新的输入覆盖

Question

您好，我的程序真的需要帮助，我到处搜索解决方案，但似乎找不到我要找的东西。

我正在制作一个程序，用户可以在其中添加桌面，为其输入各种信息，然后将其添加到数组列表中。

代码如下：

简介：

    Scanner scan = new Scanner(System.in);
    String input;
    boolean looper = true;
    DecimalFormat f = new DecimalFormat("#.00");
    ArrayList<Desktop> desktopList = new ArrayList<>();
    ArrayList<Laptop> laptopList = new ArrayList<>();

    while (looper) {
        System.out.println("");
        System.out.println("******************* Artificial Intelligence Co. *************************");
        System.out.println("1. Add Information for new Desktop");
        System.out.println("2. Add Information for new Laptop");
        System.out.println("3. Display all computer information");
        System.out.println("4. Quit");
        System.out.println("5. Credits");
        System.out.println("*************************************************************************");

Switch 语句和案例 1：

switch (input) {
            case "1":
                System.out.println("");
                System.out.println("=========================================================================");
                System.out.println("Information for new Desktop");
                System.out.println("=========================================================================");

                Desktop xx = new Desktop();
                boolean loop = true;


                while (loop) {
                    System.out.print("What is the Computer ID: ");
                    xx.setComputerID(scan.nextLine().toUpperCase());

                    if ((xx.getComputerID().startsWith("D")) && (xx.getComputerID().length() == 4)) {
                        loop = false;
                    } else {
                        System.out.println("Computer ID should start with a letter \"D\". and have 4 characters.");
                        System.out.println("");
                    }
                }

                loop = true;
                while (loop) {
                    System.out.print("What is the Processor Speed: ");
                    xx.setCPUspeed(scan.nextLine().toUpperCase());
                    try {
                        if (StringisDouble(xx.getCPUspeed().substring(0, (xx.getCPUspeed().length() - 2))) ||
                                StringisDouble(xx.getCPUspeed().substring(0, (xx.getCPUspeed().length() - 3)))) {   //checks the value before GHZ or HZ if its a double
                            if (xx.getCPUspeed().endsWith("GHZ") || xx.getCPUspeed().endsWith("HZ")) {
                                loop = false;
                            } else {
                                System.out.println("CPU Speed input should end with \"GHZ\" or \"HZ\".");
                                System.out.println("");
                            }
                        } else {
                            System.out.println("CPU Speed input should contain a decimal or number followed by  a \"GHZ\" or a \"HZ\".");
                            System.out.println("");
                        }
                    } catch (StringIndexOutOfBoundsException e) {
                        System.out.println("CPU Speed input should contain a decimal or number followed by  a \"GHZ\" or a \"HZ\".");
                        System.out.println("");
                    }

                }

                loop = true;
                while (loop) {
                    System.out.print("What is the RAM: ");
                    xx.setRAM(scan.nextLine().toUpperCase());
                    try {
                        if (StringisInteger(xx.getRAM().substring(0, (xx.getRAM().length() - 2)))) {        //checks the value if it is numeric and ending with GB or MB
                            if (xx.getRAM().endsWith("GB") || xx.getRAM().endsWith("MB")) {
                                loop = false;
                            } else {
                                System.out.println("RAM input should have a numeric value and end with \"GB\" or \"MB\".");
                                System.out.println("");
                            }
                        } else {
                            System.out.println("RAM input should have a numeric value and end with \"GB\" or \"MB\".");
                            System.out.println("");
                        }
                    } catch (StringIndexOutOfBoundsException e) {
                        System.out.println("RAM input should have a numeric value and end with \"GB\" or \"MB\".");
                        System.out.println("");
                    }


                }

                loop = true;
                while (loop) {
                    System.out.print("What is the Harddisk size: ");
                    xx.setHarddisk(scan.nextLine().toUpperCase());
                    try {
                        if (StringisInteger(xx.getHarddisk().substring(0, (xx.getHarddisk().length() - 2)))) {        //checks the value if it is numeric and ending with GB or MB
                            if (xx.getHarddisk().endsWith("GB") || xx.getHarddisk().endsWith("TB")) {
                                loop = false;
                            } else {
                                System.out.println("Harddisk input should have a numeric value and end with \"GB\" or \"TB\".");
                                System.out.println("");
                            }
                        } else {
                            System.out.println("Harddisk input should have a numeric value and end with \"GB\" or \"TB\".");
                            System.out.println("");
                        }
                    } catch (StringIndexOutOfBoundsException e) {
                        System.out.println("Harddisk input should have a numeric value and end with \"GB\" or \"TB\".");
                        System.out.println("");
                    }
                }


                loop = true;
                while (loop) {
                    System.out.print("What is the Monitor: ");
                    xx.setMonitor(scan.nextLine().toUpperCase());
                    if (xx.getMonitor().equals("CRT") || xx.getMonitor().equals("LCD")) {
                        loop = false;
                    } else {
                        System.out.println("Please enter in CRT or LCD only.");
                        System.out.println("");
                    }
                }

                loop = true;
                while (loop) {
                    try {
                        System.out.print("What is the price: $");
                        xx.setPrice(Double.parseDouble(scan.nextLine()));
                        loop = false;
                    } catch (NumberFormatException e) {
                        System.out.println("Price input should be numeric.");
                        System.out.println("");
                    }
                }

                desktopList.add(xx);

                System.out.println("Information successfully added.");
                System.out.println("");
                System.out.println("");
                break;

案例 3，用户可以看到 he/she 输入的内容：

                case "3":
                int DesktopCounter = 1;
                int LaptopCounter = 1;

                System.out.println("");
                if (desktopList.isEmpty()) {
                    System.out.println("No desktop added!");
                    System.out.println("");
                } else {
                    for (int i = 0; i < desktopList.size(); i++) {
                        System.out.println("");
                        System.out.println("Desktop " + DesktopCounter);
                        System.out.println("Computer ID: " + desktopList.get(i).getComputerID());
                        System.out.println("Processor Speed: " + desktopList.get(i).getCPUspeed());
                        System.out.println("RAM: " + desktopList.get(i).getRAM());
                        System.out.println("Harddisk:" + desktopList.get(i).getHarddisk());
                        System.out.println("Monitor: " + desktopList.get(i).getMonitor());
                        System.out.println("Price: $" + f.format(desktopList.get(i).getPrice()));
                        DesktopCounter++;
                    }
                }
                break;

桌面 Class:

       public class Desktop extends Computer //Child class of Computer
    {
        private static String Monitor;

        public Desktop()
        {
            ComputerID = "-- No ID specified --";
            CPUspeed = "-- No processor speed specified --";
            RAM = "-- No RAM specified-";
            Harddisk = "-- No Harddisk size specified --";
            Monitor = "-- No Monitor specified --";
            Price = 0.0;
        }



//Setters and Getters
    public String getMonitor()
    {
        return Monitor;
    }

    public   void setMonitor(String monitor)
    {
        Monitor = monitor;
    }


}

计算机Class:

public class Computer //Parent class

{
protected static String ComputerID;
protected static String CPUspeed;
protected static String RAM;
protected static String Harddisk;
protected static double Price;


public Computer() //Initializer
{
    ComputerID = "-- No ID specified --";
    CPUspeed = "-- No processor speed specified --";
    RAM = "-- No amount RAM specified-";
    Harddisk = "-- No Harddisk size specified --";
    Price = 0.0;
}

public Computer(String computerID, String cpuspeed, String ram, String harddisk, double price) {
    ComputerID = computerID;
    CPUspeed = cpuspeed;
    RAM = ram;
    Harddisk = harddisk;
    Price = price;


}


//Getters and Setters
public String getComputerID() {
    return ComputerID;
}

public void setComputerID(String computerID) {
    ComputerID = computerID;
}

public String getCPUspeed() {
    return CPUspeed;
}

public void setCPUspeed(String cpuspeed) {
    CPUspeed = cpuspeed;
}

public String getRAM() {
    return RAM;
}

public void setRAM(String ram) {
    RAM = ram;
}

public String getHarddisk() {
    return Harddisk;
}

public void setHarddisk(String harddisk) {
    Harddisk = harddisk;
}

public double getPrice() {
    return Price;
}

public void setPrice(double price) {
    Price = price;
}

//End of getters and setters

}

现在假设我使用案例 1 添加桌面并输入以下信息：

计算机 ID：D001
处理器速度：3.2GHZ
内存：512MB
硬盘：80GB
显示器：CRT

然后继续使用这些添加另一个桌面：

计算机 ID：D123
处理器速度：4.4GHZ
内存：8GB
硬盘：1TB
显示器：LCD

当我使用案例3代码块显示信息时，它输出：

桌面 1
计算机 ID：D123
处理器速度：4.4GHZ
内存：8GB
硬盘：1TB
显示器：LCD

桌面 2
计算机 ID：D123
处理器速度：4.4GHZ
内存：8GB
硬盘：1TB
显示器：LCD

如果正确，桌面 1 应该显示其自己的独特属性。

如有任何帮助，我将不胜感激。

编辑：我通过使我的变量成为非静态变量解决了这个问题。

Answer 1

在 posted

额外代码后更新

您的字段在 Desktop、Computer 和 Laptop class 中不应 static。更改这些字段：

protected static String ComputerID;
protected static String CPUspeed;
protected static String RAM;
protected static String Harddisk;
protected static double Price;

至

protected String ComputerID;
protected String CPUspeed;
protected String RAM;
protected String Harddisk;
protected double Price;

class 的每个对象的静态字段都相同。因此，如果您有多个桌面并且您将价格声明为静态，则所有桌面将共享相同的价格字段。这不是你想要的，显然所有台式机都有另一个价格。

也改

private static String Monitor;

至

private String Monitor;

您真的希望每台计算机都有一个单独的显示器，而不是为所有计算机共享同一个显示器。

旧答案

代码在这里运行完美，所以一定有一些缺失的信息：问题一定是在你没有的代码的某些部分post:

******************* Artificial Intelligence Co. *************************
1. Add Information for new Desktop
2. Add Information for new Laptop
3. Display all computer information
4. Quit
5. Credits
*************************************************************************
3

Desktop 1
Computer ID: D123
Processor Speed: 2GHZ
RAM: 2GB
Harddisk:1TB
Monitor: CRT
Price: 0.00

Desktop 2
Computer ID: D002
Processor Speed: 2GHZ
RAM: 16GB
Harddisk:2TB
Monitor: CRT
Price: 0.00

一些想法：

你没有post Desktop class，如果Desktop class中的字段声明为静态的，那将解释结果，确保它们没有被声明为 static
您似乎在某处使用了相同的变量，例如Desktop xx = new Desktop(); 不像上面的代码那样在 case 语句中
您可能使用了错误的索引来获取列表项，您正在使用 for-i 循环循环并执行 desktopList.get(i) 如果您碰巧执行 desktopList.get(0) 或 desktopList.get(someVariableThatIsAlwaysZero) 你将始终打印相同的结果。使用新的 foreach 语法更安全：for (Desktop desktop : desktopList){ ... }
你必须学会使用调试器，一步一步地检查代码，看看在哪里插入了重复值，如果没有插入重复值，看看打印语句在哪里打印以及它们打印的原因相同的值；使用调试器对于发现问题非常重要
您的代码可能不同步

我只会给你我的版本，所以你可能想要比较：

public static void main(String args[]) {

        Scanner scan = new Scanner(System.in);
        String input;
        boolean looper = true;
        DecimalFormat f = new DecimalFormat("#.00");
        ArrayList<Desktop> desktopList = new ArrayList<>();
        ArrayList<Laptop> laptopList = new ArrayList<>();

        while (looper) {
            System.out.println("");
            System.out.println("******************* Artificial Intelligence Co. *************************");
            System.out.println("1. Add Information for new Desktop");
            System.out.println("2. Add Information for new Laptop");
            System.out.println("3. Display all computer information");
            System.out.println("4. Quit");
            System.out.println("5. Credits");
            System.out.println("*************************************************************************");

            input = scan.nextLine();

            switch (input) {
                case "1":
                    System.out.println("");
                    System.out.println("=========================================================================");
                    System.out.println("Information for new Desktop");
                    System.out.println("=========================================================================");

                    Desktop xx = new Desktop();
                    boolean loop = true;


                    while (loop) {
                        System.out.print("What is the Computer ID: ");
                        xx.setComputerID(scan.nextLine().toUpperCase());

                        if ((xx.getComputerID().startsWith("D")) && (xx.getComputerID().length() == 4)) {
                            loop = false;
                        } else {
                            System.out.println("Computer ID should start with a letter \"D\". and have 4 characters.");
                            System.out.println("");
                        }
                    }

                    loop = true;
                    while (loop) {
                        System.out.print("What is the Processor Speed: ");
                        xx.setCPUspeed(scan.nextLine().toUpperCase());
                        try {
                            if (StringisDouble(xx.getCPUspeed().substring(0, (xx.getCPUspeed().length() - 2))) ||
                                    StringisDouble(xx.getCPUspeed().substring(0, (xx.getCPUspeed().length() - 3)))) {   //checks the value before GHZ or HZ if its a double
                                if (xx.getCPUspeed().endsWith("GHZ") || xx.getCPUspeed().endsWith("HZ")) {
                                    loop = false;
                                } else {
                                    System.out.println("CPU Speed input should end with \"GHZ\" or \"HZ\".");
                                    System.out.println("");
                                }
                            } else {
                                System.out.println("CPU Speed input should contain a decimal or number followed by  a \"GHZ\" or a \"HZ\".");
                                System.out.println("");
                            }
                        } catch (StringIndexOutOfBoundsException e) {
                            System.out.println("CPU Speed input should contain a decimal or number followed by  a \"GHZ\" or a \"HZ\".");
                            System.out.println("");
                        }

                    }

                    loop = true;
                    while (loop) {
                        System.out.print("What is the RAM: ");
                        xx.setRAM(scan.nextLine().toUpperCase());
                        try {
                            if (StringisInteger(xx.getRAM().substring(0, (xx.getRAM().length() - 2)))) {        //checks the value if it is numeric and ending with GB or MB
                                if (xx.getRAM().endsWith("GB") || xx.getRAM().endsWith("MB")) {
                                    loop = false;
                                } else {
                                    System.out.println("RAM input should have a numeric value and end with \"GB\" or \"MB\".");
                                    System.out.println("");
                                }
                            } else {
                                System.out.println("RAM input should have a numeric value and end with \"GB\" or \"MB\".");
                                System.out.println("");
                            }
                        } catch (StringIndexOutOfBoundsException e) {
                            System.out.println("RAM input should have a numeric value and end with \"GB\" or \"MB\".");
                            System.out.println("");
                        }


                    }

                    loop = true;
                    while (loop) {
                        System.out.print("What is the Harddisk size: ");
                        xx.setHarddisk(scan.nextLine().toUpperCase());
                        try {
                            if (StringisInteger(xx.getHarddisk().substring(0, (xx.getHarddisk().length() - 2)))) {        //checks the value if it is numeric and ending with GB or MB
                                if (xx.getHarddisk().endsWith("GB") || xx.getHarddisk().endsWith("TB")) {
                                    loop = false;
                                } else {
                                    System.out.println("Harddisk input should have a numeric value and end with \"GB\" or \"TB\".");
                                    System.out.println("");
                                }
                            } else {
                                System.out.println("Harddisk input should have a numeric value and end with \"GB\" or \"TB\".");
                                System.out.println("");
                            }
                        } catch (StringIndexOutOfBoundsException e) {
                            System.out.println("Harddisk input should have a numeric value and end with \"GB\" or \"TB\".");
                            System.out.println("");
                        }
                    }


                    loop = true;
                    while (loop) {
                        System.out.print("What is the Monitor: ");
                        xx.setMonitor(scan.nextLine().toUpperCase());
                        if (xx.getMonitor().equals("CRT") || xx.getMonitor().equals("LCD")) {
                            loop = false;
                        } else {
                            System.out.println("Please enter in CRT or LCD only.");
                            System.out.println("");
                        }
                    }

                    loop = true;
                    while (loop) {
                        try {
                            System.out.print("What is the price: $");
                            xx.setPrice(Double.parseDouble(scan.nextLine()));
                            loop = false;
                        } catch (NumberFormatException e) {
                            System.out.println("Price input should be numeric.");
                            System.out.println("");
                        }
                    }

                    desktopList.add(xx);

                    System.out.println("Information successfully added.");
                    System.out.println("");
                    System.out.println("");
                    break;

                case "3":
                    int DesktopCounter = 1;
                    int LaptopCounter = 1;

                    System.out.println("");
                    if (desktopList.isEmpty()) {
                        System.out.println("No desktop added!");
                        System.out.println("");
                    } else {
                        for (int i = 0; i < desktopList.size(); i++) {
                            System.out.println("");
                            System.out.println("Desktop " + DesktopCounter);
                            System.out.println("Computer ID: " + desktopList.get(i).getComputerID());
                            System.out.println("Processor Speed: " + desktopList.get(i).getCPUspeed());
                            System.out.println("RAM: " + desktopList.get(i).getRAM());
                            System.out.println("Harddisk:" + desktopList.get(i).getHarddisk());
                            System.out.println("Monitor: " + desktopList.get(i).getMonitor());
                            System.out.println("Price: $" + f.format(desktopList.get(i).getPrice()));
                            DesktopCounter++;
                        }
                    }
                    break;
            }
        }
    }

    private static boolean StringisInteger(String substring) {return true;}

    private static boolean StringisDouble(String substring) { return true; }

我的桌面 class 看起来像这样：

@Data
public class Desktop {

    private double price;
    private String computerID;
    private String CPUspeed;
    private String RAM;
    private String harddisk;
    private String monitor;

}

其中 @Data 是生成 setter 和 getter 的 Lombok 注释。如您所见，字段不是静态的。

以前的输入被较新的输入覆盖

Previous Input gets overwritten by Newer Input

java

loops

overwrite

while-loop

switch-statement