// MyCls
class MyCls implements Seriliazable
{
public String mValue;
}


// ActivityA
MyCls mMyCls;
// 跳轉到ActivityB
Intent intent = new Intent();
mMyCls = new MyCls();
mMyCls.mValue = "ActivityA";
intent.putSerializable("MyCls", mMyCls);
intent.setClass(this, ActivityB.class);
startActivity(intent);

// ActivityB
MyCls cls = (MyCls)getIntent().getSerializable("MyCls");
cls.mValue = "ActivityB";