Java programming with android SDK and Eclipse

Question

I am working on a android project using the android sdk and eclipse. I am having problems with my java code so I was wondering if anyone who knows Java can you help me with my code?

Here is my code. These are where im having problems error ->

public class MainActivity extends ActionBarActivity {

    private static final String R = null;
    int counter;
    Button add, sub;
    TextView display;

    @Override
    public void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
error ->   setContentView(R.layout.activity_main);
           counter = 0;
error ->    add = (Button) findViewById(R.id.button1);
error ->    sub = (Button) findViewById(R.id.button2);
error ->   display = (TextView) findViewById(R.id.text);
           add.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                counter++;
                display.setText("Your Total is" + counter);
            }
        });
        sub.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                counter--;
                display.setText("Your total is " + counter);
            }
        });
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
error ->   getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.`enter code here`
        int id = item.getItemId();
error ->     if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

Answer 1

Remove private static final String R = null; and add an import for android.R :

import android.R;

You're trying to call methods on the android.R class, but you're not importing it correctly and trying to declare a static field with the same name as a String instead. This makes your compiler sad.