Question

    public static void main(String[] args)
{
    CollegeTester ct = new CollegeTester();
    ct.getCommand();//goes to command
}   

//Ask user for a command
public void getCommand()
{
    String command = "";
    System.out.println("Enter a command: ");
    command = input.nextLine();
        if(command.equals("add"))
            addCommand();//If command is add go to addCommand
        if(command.equals("course"))
            courseCommand();//If command is course go to courseCommand
        if(command.equals("find"))
            findCommand();
        if(command.equals("remove"))
            removeCommand();
        if(command.equals("highest"))
            highestCommand();
        if(command.equals("login"))
            loginCommand();
        if(command.equals("quit"))
            System.exit(1);
}

我想重复getCommand（）方法，直到用户输入quit但它总是失败

我试图将getCommand（）放在每个其他方法的末尾＆amp; if语句不会重复
我试图为所有事情做一个while循环，但如果有人意外地输入错误类型退出程序永远不会结束

在用户希望退出之前，我将如何有效地返回此方法？

Answer 1

我会用两种方法之一。

public static void main(String[] args)
{
    CollegeTester ct = new CollegeTester();
    ct.getCommand();//goes to command

}  

//Ask user for a command
public void getCommand()
{
    boolean exit = false;
    while(!exit){
        String command = "";
        System.out.println("Enter a command: ");
        command = input.nextLine();
            if(command.equals("add")){
                addCommand();//If command is add go to addCommand
            }else if(command.equals("course")){
                courseCommand();//If command is course go to courseCommand
            }else if(command.equals("find")){
                findCommand();
            }else if(command.equals("remove")){
                removeCommand();
            }else if(command.equals("highest")){
                highestCommand();
            }else if(command.equals("login")){
                loginCommand();
            }else if(command.equals("quit")){
                exit = true;
            }else {
                System.out.println("Not valid command, try again.");
            }
    }

}



//Ask user for a command
public void getCommand()
{
    while(true){
        String command = "";
        System.out.println("Enter a command: ");
        command = input.nextLine();
            if(command.equals("add"))
                addCommand();//If command is add go to addCommand
            if(command.equals("course"))
                courseCommand();//If command is course go to courseCommand
            if(command.equals("find"))
                findCommand();
            if(command.equals("remove"))
                removeCommand();
            if(command.equals("highest"))
                highestCommand();
            if(command.equals("login"))
                loginCommand();
            if(command.equals("quit"))
                System.exit(0);  // or could use 'break' here (thanks Mikkel)
    }

}

编辑：更正了System.exit（1）。谢谢Mikkel。

Answer 2

或者你可以把它放在while循环中：

while(true) {
    getCommand();
}

另外，请查看this question on System.exit(int)，您实际上是说应用程序应该因为错误而关闭。如果要关闭，您应该通过0，而不是1。

事实上，如果你使用像上面这样的while循环，我可能只是通过return false;或其他东西逃避循环，让程序自然结束。

重复虚空方法

2 个答案: