An Example of Java Interface

CloudService.java

public class CloudService {

    // LoginCallback interface
    static public interface LoginCallback {
        public void onSuccess(final String loginId, final String token);
        public void onFailure(final String loginId, final int errorCode);
    }
    
    // login method
    static public void login(
        final String id,
        final String password,
        final LoginCallback loginCallback) {

        if (id == null || password == null) {
            loginCallback.onFailure(id, -1);   // TypeError = -1
            return;
        }

        // Query from cloud server
        if (id.equals("zlargon") && password.equals("123")) {
            loginCallback.onSuccess(id, "token:zlargon:123");
            return;
        }

        // Http Timeout = -2
        // Wrong Username/password = -3
        loginCallback.onFailure(id, -3);
    }
}

Example.java

public class Example {
    public static void main(String [] args) {

        CloudService.login("zlargon", "123", new CloudService.LoginCallback() {
            @Override
            public void onSuccess(final String loginId, final String token) {
                System.out.println("Login success: token = " + token);
            };

            @Override
            public void onFailure(String loginId, int errorCode) {
                System.out.println("Login failure: error code = " + errorCode);
            };
        });

    }
}

Example2.java

public class Example2 {
    public static void main(String [] args) {
        MyCallback myCallback = new MyCallback();
        CloudService.login("zlargon", "000", myCallback);
    }
}

class MyCallback implements CloudService.LoginCallback {
    @Override
    public void onSuccess(final String loginId, final String token) {
        System.out.println("Login success: token = " + token);
    };

    @Override
    public void onFailure(String loginId, int errorCode) {
        System.out.println("Login failure: error code = " + errorCode);
    };
}

How to build

$ rm *.class
$ javac *.java

Run Example

$ java Example
$ java Example2