JAVA

android studio start activity

startActivity(new Intent(getApplicationContext(), newActivity.class));

start new activity android

startActivity(new Intent(getApplicationContext(), ActivityName.class));

android start new Activity from an activity with a child

val newIntent = Intent(this@Activity1, Activity2::class.java)
newIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK)
newIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)

this@Activity1.startActivity(newIntent)