out.println 说 out 无法解决

Question

When I write out.println() , eclipse complains that out cannot be resolved.

I have imported java.io.* and other servlet packages.

Answer 1

Just a shot in the dark, I think this is the out you are looking for:

public class OutServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        PrintWriter out = response.getWriter();
        out.println("foo");
    }
}

Answer 2

You should write System.out.println(); inside a function.

If you write it directly into the class then it might show the error that you are having right now.

Answer 3

采用：

import static java.lang.System.out;

Answer 4

Import it using a static import:

    import static java.lang.System.out;

However, I'd recommend that you don't do this.

• Using the full name makes references to System.out stand out, and makes them easier to "grep" for ... if you need to nuke traceprints.

• If you need to write a lot of stuff to the console, you should make out a variable or a method parameter. This will help to make your code more reusable; eg so that it can write to somewhere other than System.out .

Answer 5

I had this problem. I found out I didn't have main method( public static void main(string[]args) and that is why it was giving me this error. Hope this helps.

Answer 6

If your are looking to put some debug outputs, you can do this:

System.out.println("foo");

If your are looking for adding the output to HTML not printing on debug console you can do as follow: First you should add the 'servlet-api.jar' to your project. Then simply you can use this if you want to add your output to HTML:

response.getWriter().println("foo");

I hope it helps.

Answer 7

Can you please check whether you are having any class name as "System" ? This could be the one reason. Like in the code below if I use class name as System it would end up with the same Error like yours.

********** Cannot use Identifier 'System' as Class name;**********

public class System {

public static void main(String[] args) {

    int A[] = { 3, 9, 7, 8, 12, 6, 15, 5, 4, 10 };

    for (int x : A) {
        System.out.print(x + ", ");

    }
    System.out.println("\n*******************");
    int t = A[A.length - 1];

    System.out.println(t);

}

}