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来源: 互联网 发布时间：2015-06-22
本文导语: 题目如下： Assume the class AcLis implements the ActionListener interface. The code fragment below constructs a button and gives it four action listeners. When the button is pressed, which action listener is the first to get its actionPerform...
题目如下：
Assume the class AcLis implements the ActionListener interface. The code fragment below constructs a button and gives it four
action listeners. When the button is pressed, which action listener is the first to get its actionPerformed() method invoked?
1. Button btn = new Button("Hello");
2. AcLis a1 = new AcLis();
3. AcLis a2 = new AcLis();
4. AcLis a3 = new AcLis();
5. btn.addActionListener(a1);
6. btn.addActionListener(a2);
7. btn.addActionListener(a3);
8. btn.removeActionListener(a2);
9. btn.removeActionListener(a3);
10. btn.addActionListener(a3);
11. btn.addActionListener(a2);
答案（单选）
a: a1 gets its actionPerformed() method invoked first.
b: a2 gets its actionPerformed() method invoked first.
c: a3 gets its actionPerformed() method invoked first.
d: It is impossible to know which listener will be first.
Assume the class AcLis implements the ActionListener interface. The code fragment below constructs a button and gives it four
action listeners. When the button is pressed, which action listener is the first to get its actionPerformed() method invoked?
1. Button btn = new Button("Hello");
2. AcLis a1 = new AcLis();
3. AcLis a2 = new AcLis();
4. AcLis a3 = new AcLis();
5. btn.addActionListener(a1);
6. btn.addActionListener(a2);
7. btn.addActionListener(a3);
8. btn.removeActionListener(a2);
9. btn.removeActionListener(a3);
10. btn.addActionListener(a3);
11. btn.addActionListener(a2);
答案（单选）
a: a1 gets its actionPerformed() method invoked first.
b: a2 gets its actionPerformed() method invoked first.
c: a3 gets its actionPerformed() method invoked first.
d: It is impossible to know which listener will be first.
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应该是d
类似多线程问题,多个相同的listenser同时加载时,当响应click时,如同在线程池中唤醒某个处于waiting状态的线程,不能确定哪个被最先执行.
类似多线程问题,多个相同的listenser同时加载时,当响应click时,如同在线程池中唤醒某个处于waiting状态的线程,不能确定哪个被最先执行.
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选择d,无法确定。你可以写一段代码试试，给予监听器不同的动作，多次执行，一定不同的结果。
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