This is very important tutorial to READ EXISTING CONTACTS from device contacts list .There are some following steps to do this process.

Step-1 - Add a permission to open and read contacts from contacts list to your manifest xml file.

 <uses-permission android:name="android.permission.READ_CONTACTS"/>

Step-2- Create an Intent that ask the system to start an Activity that perform Pick action.

Intent intent = new Intent(Intent.ACTION_PICK, ContactsContract.Contacts.CONTENT_URI);
startActivityForResult(intent, PICK_CONTACT);

Step-3- In your Activity override onActivityResult() to listen for the result respond from Step-2 code. Here is complete Activity code.

import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.ContactsContract;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity implements OnClickListener {

    private static final int PICK_CONTACT = 0;
    Button button;
    TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button=(Button)findViewById(R.id.pic_contacts);
        button.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub

        Intent intent = new Intent(Intent.ACTION_PICK, ContactsContract.Contacts.CONTENT_URI);
        startActivityForResult(intent, PICK_CONTACT);

    }
    @Override
    public void onActivityResult(int reqCode, int resultCode, Intent data) {
    super.onActivityResult(reqCode, resultCode, data);

    switch (reqCode) {
    case (PICK_CONTACT) :
      if (resultCode == Activity.RESULT_OK) {
        Uri contactData = data.getData();
        Cursor c =  managedQuery(contactData, null, null, null, null);
        if (c.moveToFirst()) {
          @SuppressWarnings("deprecation")
            String name=c.getString(c.getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME));

          Log.d("Contacts Name", name);
          textView=(TextView)findViewById(R.id.contacts_name);
          textView.setText(name.toString());
          // TODO Whatever you want to do with the selected contact name.
        }
      }
      break;
    }
    }
}

Step-4- Create an XML file .

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <Button
        android:id="@+id/pic_contacts"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Pic Contacts" >
    </Button>

    <TextView
        android:id="@+id/contacts_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/pic_contacts"
        android:textSize="15dp" />

</RelativeLayout>