在编译我的简单Java文件时出现编译错误

Question

I have written a simple java program mentioned in below. Unfortunately a compile error occurs.

class String {
    public static void main(String[] args) {
         System.out.println("stre");
    }
}

The following comes out during compilation at command prompt:

c:\\Java>java String Error: Main method not found in class String, please define the main method as: public static void main(String[] args)

It wasn't working for any of my programs, not even this simple one! Why is this?

EDIT:

Now I have:

import java.lang.*;
import java.lang.String.*;

class incogn {
    public static void main(String[] args) {
        System.out.println("stre");
    }
}

And its not working. Why isn't that working?

It says the exact thing as before.

What you said with the Java.lang.String[] works, but why won't this? And why haven't I needed to put any of this on before?

Answer 1

It's probably because you are using the name String for your class, colliding with java.lang.String ; in other words, you have written that your main method takes instances of your class as input, rather than the one that the main method needs to take, namely java.lang.String . Try either

1. Renaming your class
2. Changing your signature to public static void main(java.lang.String[] args) {

Answer 2

Well, giving your class name String and then call main(String[] args) is ambiguous, if it means java.lang.String or your newly defined class, but with java scope rules, it will use your, unless otherwise declared.

---

Update after edit

There's no java.lang.String package , but it is a class . Therefore, you can't say

import java.lang.String.*;

By adding the " .* " the compiler understands that this refers to some package String .

One exception, is the static import, but this is not what you need here.

Answer 3

You should not call your class String, it will conflict with the java class String.

Or, you can change your code to:

class String {
    public static void main(java.lang.String[] args) {
         System.out.println("stre");
    }
}

Answer 4

1. Don't create a java file named "String" as it is the java library class in java.lang.String
2. Make the class as public

So, write your source code as below:

public class StringDemo {
    public static void main(String[] args) {
         System.out.println("stre");
    }
}

Compile it now. I believe it would work well.

Answer 5

1) The class should be public

2) Avoid to call you class String , as it has the duplicate name with java.lang.String (You still can, but not good). Otherwise, your main method is having wrong type of arguments.

3) You don't have to explicitly import from java.lang package.

---

public class String {
    public static void main(java.lang.String[] args) {
         System.out.println("stre");
    }
}

OR

public class YourClass {
    public static void main(String[] args) {
         System.out.println("stre");
    }
}

Try to use the second form.