用Intent传递对数

1  public void onClick(View v) {
2                Intent intent=new Intent(MainActivity.this, SecondActivity.class);
3                intent.putExtra("extra_data","Hello world");
4                intent.putExtra("age",15);
5                startActivity(intent);

        Intent intent=getIntent();
        String a=intent.getStringExtra("extra_data");
        Log.d("SecondActivity",a);