simple App it is change text color

onClickListener.java

// see http://imgur.com/a/cjk7N

package com.ahmad.mustafa.exercises;

import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;


public class MainActivity extends AppCompatActivity
{
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        Button blue =(Button) findViewById(R.id.Blue_Button);
        blue.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                buttonClicked(v);
            }
        });

        Button  green = (Button)findViewById(R.id.Green_Button);
        green.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
               buttonClicked(v);
            }
        });

        Button red = (Button)findViewById(R.id.Red_Button);
        red.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                buttonClicked(v);
            }
        });
        
    }
    protected void buttonClicked(View view)
    {
        TextView o = (TextView)findViewById(R.id.o_TextView);
        switch (view.getId()){
            case (R.id.Blue_Button) :
                o.setTextColor(Color.BLUE);
                break;
            case (R.id.Green_Button) :
                o.setTextColor(Color.GREEN);
                break;
            case (R.id.Red_Button) :
                o.setTextColor(Color.RED);
                break;
            default:

                break;
        }
       
    }
}