求教toast显示有关问题~_Android

求教toast显示问题~~
有两个java文件
第一个是

Java code

package com.helloworld;import android.app.Activity;import android.content.Context;import android.os.Bundle;import android.widget.Toast;public class HelloworldActivity extends Activity {    static Context o;    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //setContentView(R.layout.main);        String n="number1";        Context o=getApplicationContext();        Toast.makeText(o, n,        Toast.LENGTH_LONG).show();        hello.on();    }}

第二个文件是

Java code

package com.helloworld;import android.app.Application;import android.content.Context;import android.widget.Toast;public class hello extends Application {        Context aa;    public static void on() {        String n="number2";        Toast.makeText(HelloworldActivity.o, n,        Toast.LENGTH_LONG).show();    }}

为什么模拟器里运行强制关闭~~~到底有什么问题，小弟是新学。请各位大神不吝赐教~~~

------解决方案--------------------
这一句要改一下
Context o=getApplicationContext();
改成
o=getApplicationContext();