1.
mouse clicked與 mouse pressed 的區別
前者是在同一個位置press和release才觸發事件，執行操作. 如果在用戶一個位置按下鼠標后改變了主意，則移動到另一個位置（按鈕外面）放開就會取消操作（不執行操作）.
而后者只是觸發press事件, 也就是說按下鼠標就執行操作
2.
The text field fires three events: a key-pressed event, a key-typed event, and a key-released event.
Note :
the key-typed event doesn't have key code information.
key-pressed and key-released events don't have key character information.
用來檢驗text changed可以用key-released events. 因為它能夠通過getText（）得到textfield中改變后的text. 而 key-pressed event, key-typed event 得到的是改變前的文字
Press and release the Shift key.
The text field fires two events: a key-pressed and a key-released. The text field doesn't fire a key-typed event because Shift, by itself, doesn't correspond to any character.
Type an uppercase 'A' by pressing the Shift and A keys.
You'll see the following events, although perhaps not in this order: key-pressed (Shift), key-pressed (A), key typed ('A'), key-released (A), key-released (Shift). Note that Shift is listed as the modifier key for the key-typed and key-pressed events.
Type an uppercase 'A' by pressing and releasing the Caps Lock key, and then pressing the A key.
You should see the following events: key-pressed (Caps Lock), key-pressed (A), key typed ('A'), key-released (A). Note that Caps Lock is not listed as a modifier key.
Press the Tab key. No Tab key-pressed or key-released events are received by the key event listener. This is because the focus subsystem consumes focus traversal keys, such as Tab and Shift Tab. Press Tab twice more to return the focus to the text area.
Press a function key, such as F3. You'll see that the function key is an action key.
Press the left Shift key, followed by the right Shift key. The key-pressed and key-released events indicate which Shift key was typed.
Press the Num Lock key if your keyboard has a number pad. As for Caps Lock, there is a key-pressed event, but no key-released event.
Press the '2' key on the number pad. You see the key-pressed, key-typed, and key-released events for the number '2'.
Press the '2' key on the standard keyboard. Again, you see the three event messages. The key-typed events for both number 2 keys are identical same as press in number pad. But the key-pressed and key-released events indicate different key codes and different key locations.
Press the Num Lock key again. A key-released event is fired.