Java 从 if/if else 语句中调用方法

Calling a method from within an if/if else statement

提问by Joe Perkins

Is it possible to call a method within an if statement, and then a separate method in an if else statement?

是否可以在 if 语句中调用一个方法，然后在 if else 语句中调用一个单独的方法？

I have created a scanner than reads keyboard input, and based on the option the user gives, a different method will be called. Can I say something along the lines of:

我创建了一个扫描仪而不是读取键盘输入，并且根据用户提供的选项，将调用不同的方法。我可以说一些类似的话：

Scanner in = new Scanner (System.in);
char choice = in.next().charAt(0);

if(choice == 1)
{
    private static void doAddStudent(Student aStudent) 
    {
        this.theRegistry.addStudent(aStudent);
    }
}

any help would be much appreciated

任何帮助将非常感激

采纳答案by Philipp Sander

You can of course call a method within an if or else block. But what you tried in your snippet is DECLARING a method within a block which is impossible.

您当然可以在 if 或 else 块中调用方法。但是您在代码片段中尝试的是在块中声明一个方法，这是不可能的。

fixed snippet:

固定片段：

Scanner in = new Scanner (System.in);
char choice = in.next().charAt(0);

if(choice == 1)
{
    this.theRegistry.addStudent(aStudent);
}

EDIT:

编辑：

I think the code you want looks something like this:

我认为您想要的代码如下所示：

public static void main(String[] args) {
    //some code
    Scanner in = new Scanner (System.in);
    char choice = in.next().charAt(0);

    if(choice == 1)
    {
        RegistryInterface.doAddStdent(student);
    }
    //some code
}

The RegistryInterface.java

RegistryInterface.java

public class RegistryInterface {
    private static void doAddStudent(Student aStudent) {
        this.theRegistry.addStudent(aStudent);
    }
}

回答by Alya'a Gamal

Yes , create your method first , and then call them inside the ifstatement , Like this:

是的，先创建你的方法，然后在if语句中调用它们，像这样：

private static void doAddStudent(Student aStudent) 
        {
            this.theRegistry.addStudent(aStudent);
        }

then

然后

 if(choice == 1)
    {
        doAddStudent(aStudent) ;////here you call the doAddStudent method

    }

回答by rzymek

In your code you're not just calling a method inside the ifstatement - you're trying to define a new method. And this is illegal.

在您的代码中，您不仅仅是在if语句中调用一个方法- 您正在尝试定义一个新方法。这是非法的。

I'm guessing you want something like this:

我猜你想要这样的东西：

Scanner in = new Scanner (System.in);
char choice = in.next().charAt(0);
if(choice == '1') {
    this.theRegistry.addStudent(aStudent);
}

Also note that you were comparing char choiseagainst an int 1. I suppose you want to compare against char '1'

另请注意，您正在char choise与 int进行比较1。我想你想和 char 比较'1'

回答by rahul maindargi

Calling method is static

调用方法是静态的

static TheRegistryClass theRegistry;
static void callingMethod(){
/// Some code here 
Scanner in = new Scanner (System.in);
    char choice = in.next().charAt(0);

    if(choice == 1)
    {
       doAddStudent(aStudent);
    }

//remaining code here 

}

The method called in if block Declard in same class but outside of calling method

if block 中调用的方法声明在同一个类中但在调用方法之外

 private static void doAddStudent(Student aStudent) 
        {
            theRegistry.addStudent(aStudent); // static methods do not have reference to this
        }

if Caller Method is non Static TheRegistryClass theRegistry; void callingMethod(){ /// Some code here Scanner in = new Scanner (System.in); char choice = in.next().charAt(0);

如果调用方方法是非静态的 TheRegistryClass theRegistry; void callMethod(){ /// 这里有一些代码 Scanner in = new Scanner (System.in); 字符选择 = in.next().charAt(0);

    if(choice == 1)
    {
       doAddStudent(aStudent);
    }

//remaining code here 

}



 private static void doAddStudent(Student aStudent) 
        {
            this.theRegistry.addStudent(aStudent); // this is optional
        }

回答by Mika

Well you can.

你可以。

Scanner in = new Scanner (System.in);
char choice = in.next().charAt(0);

if(choice == 1)
    this.theRegistry.addStudent(aStudent);
else if choice == 2)
    this.theRegistry.removeStudent(aStudent);
else
    System.out.println("Please enter a valid choice.");