Android finish All activity

//关闭当前activity方法一  
  finish();  

//关闭当前界面方法二  
  android.os.Process.killProcess(android.os.Process.myPid());  

//关闭当前界面方法三  
  System.exit(0);  

//关闭当前界面方法四  
  this.onDestroy();  

Intent intent = new Intent();  
intent.setClass(DActivity.this,BActivity.class);  
intent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);//设置不要刷新将要跳到的界面  
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);//它可以关掉所要到的界面中间的activity  
startActivity(intent);  

Intent intent = new Intent();  
intent.setClass(DActivity.this,BActivity.class);  
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);//它可以关掉所要到的界面中间的activity  
startActivity(intent);  

Intent intent1 = new Intent(DActivity.this, BActivity.class);
intent1.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
startActivity(intent1);

/**
 *
 *  一个类 用来结束所有后台activity
 *
 */
public class SysApplication extends Application {  
    //运用list来保存们每一个activity是关键  
    private List<Activity> mList = new LinkedList<Activity>();  
    //为了实现每次使用该类时不创建新的对象而创建的静态对象  
    private static SysApplication instance;
    //构造方法  
    private SysApplication(){}  
    //实例化一次  
    public synchronized static SysApplication getInstance(){
        if (null == instance) {
            instance = new SysApplication();
        }
        return instance;
    }
    // add Activity
    public void addActivity(Activity activity) {
        mList.add(activity);
    }
    //关闭每一个list内的activity  
    public void exit() {
        try {
            for (Activity activity:mList) {
                if (activity != null)
                    activity.finish();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            System.exit(0);
        }
    }
    //杀进程  
    public void onLowMemory() {
        super.onLowMemory();
        System.gc();
    }
}  

//将该activity添加到list中去。
SysApplication.getInstance().addActivity(this);

//关闭整个程序  
SysApplication.getInstance().exit();