Setting the default button
Only one button in a top-level container can be the default button. The default button typically has a highlighted appearance and acts as though clicked whenever the top-level container has the keyboard focus and the user presses the Enter (or Return) key. The Exact Implementation Depends on The Look and Feel.
Say that converterframe.getrootpane (). SetdefaultButton (ConvertTemp); where ConvertTemp is a Button, saying that a top-level can only have a default button, which is high, and as long as the window is focused, there is a little doubty. , But I tested, when there is 2 Button, the button set to be defaultbutton is nothing difference with another than one. ? ? why? Don't understand
