Android and HashMap/Hashtable (Java)

package com.myapp;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class MainActivity extends Activity {

	ArrayAdapter<String> adapter;
	
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
 
        /**** Sample HashMap ****/ 
        HashMap<String,String> map = new HashMap<String,String>();

		map = new HashMap<String, String>();
		map.put("MemberID", "1");
		map.put("Name", "Weerachai");
		map.put("Tel", "0819876107");
		
        // Get Size HashMap
        final TextView txtView1 = (TextView)findViewById(R.id.textView1); 
        txtView1.setText("HashMap Size = " + map.size());
        
        // Loop Data HashMap
        final TextView txtView2 = (TextView)findViewById(R.id.textView2); 
        txtView2.setText("");
        Iterator<String> Vmap = map.keySet().iterator();
	 	while(Vmap.hasNext()){
		 	String key = (String)(Vmap.next());  // Key
		 	String val = map.get(key); // Value
		 	txtView2.setText(txtView2.getText() + key + "=" + val + ",\r\n");
	 	}
	 	
	 	map.clear();
	 	
	 	
	 	
	 	
	 	 /**** Sample Hashtable ****/ 
	 	Hashtable<String,String> table = new Hashtable<String,String>();

        table = new Hashtable<String, String>();
        table.put("MemberID", "2");
        table.put("Name", "Win");
        table.put("Tel", "021978032");
        
        // Get Size Hashtable
        final TextView txtView3 = (TextView)findViewById(R.id.textView3); 
        txtView3.setText("Hashtable Size = " + table.size());
        
        // Loop Data Hashtable
        final TextView txtView4 = (TextView)findViewById(R.id.textView4); 
        txtView4.setText("");
        Iterator<String> Vtable = table.keySet().iterator();
	 	while(Vtable.hasNext()){
		 	String key = (String)(Vtable.next());  // Key
		 	String val = table.get(key); // Value
		 	txtView4.setText(txtView4.getText() + key + "=" + val + ",\r\n");
	 	}
	 	
	 	table.clear();
        
    }
    
    
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
	
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:orientation="horizontal"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:layout_weight="0.1">   
   
   <ListView
       android:id="@+id/listView1"
       android:layout_width="match_parent"
       android:layout_height="wrap_content">
   </ListView>
	        
</LinearLayout>