Couldn't resolve resource @string/app_name - Android Q&A, Help & Troubleshooting

Hi Everyone.. I'm a beginner in Android programming, I have a problem in string reference. Please help.. Thanks
Here's my code..
activity_main.xml
Code:
<LinearLayout xmlns:android="h t t p : / / schemas . android . com / apk / res / android"
xmlns:tools="h t t p : / / schemas . android . com / tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >
<TextView
android:id="@+id/tvDisplay"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/score"
android:textSize="45sp"
android:layout_gravity="center"
android:gravity="center" />
<Button
android:id="@+id/bAdd"
android:layout_width="250dp"
android:layout_height="wrap_content"
android:text="@string/add"
android:layout_gravity="center"
android:textSize="20sp" />
<Button
android:id="@+id/bSub"
android:layout_width="250dp"
android:layout_height="wrap_content"
android:text="@string/sub"
android:layout_gravity="center"
android:textSize="20sp" />
</LinearLayout>
string.xml
Code:
display.setText("Your total is " + counter);<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">My First App</string>
<string name="action_settings">Settings</string>
<string name="score">Your Score is 0</string>
<string name="add">Add one</string>
<string name="sub">Subtract one</string>
</resources>
MainActivity.java
Code:
package com.ben.myfirstapp;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends Activity {
int counter;
Button add, sub;
TextView display;
[user=439709]@override[/user]
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
counter = 0;
add = (Button)findViewById(R.id.bAdd);
sub = (Button)findViewById(R.id.bSub);
display = (TextView)findViewById(R.id.tvDisplay);
add.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
counter++;
display.setText("Your total is " + counter);
}
});
sub.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
counter--;
display.setText("Your total is " + counter);
}
});
}
[user=439709]@override[/user]
public boolean onCreateOptionsMenu(Menu menu)
{
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}

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Here's a screenshot of the Graphic Layout..

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Issue is in your string.xml file... The first line remove
>>> display.setText("...);<<< and it should work