黑马程序员入学测试题答案.docxVIP

1.定义一个交通灯枚举，包含红灯、绿灯、黄灯，需要有获得下一个灯的方法;例如：红灯获取下一个灯是绿灯，绿灯获取下一个灯是黄灯。publicenum Lamp {RED(GREEN),GREEN(YELLOW),YELLOW(RED);private String next;private Lamp(String next){this.next = next;}public Lamp nextLamp(){returnLamp.valueOf(next); }}2、写一个ArrayList类的代理，实现和ArrayList中完全相同的功能，并可以计算每个方法运行的时间。publicclass test1 {publicstaticvoid main(String[] args) {finalArrayList target = newArrayList();List proxy = (List)Proxy.newProxyInstance(List.class.getClassLoader(), ArrayList.class.getInterfaces(), newInvocationHandler() {@Overridepublic Object invoke(Object proxy, Method method, Object[] args)throwsThrowable {longbeginTime = System.currentTimeMillis();Thread.sleep(10);Object reVal = method.invoke(target, args);longendTime = System.currentTimeMillis();System.out.println(method.getName()+ runing time is +(endTime-beginTime));returnreVal;}});proxy.add(nihaoa);proxy.add(nihaoa);proxy.add(nihaoa);proxy.remove(nihaoa);System.out.println(proxy.toString());}}3. ArrayList list = new ArrayList();在这个泛型为Integer的ArrayList中存放一个String类型的对象。publicclass test2 {publicstaticvoid main(String[] args) throws Exception{ArrayListInteger list = newArrayListInteger();Method method = list.getClass().getMethod(add, Object.class);method.invoke(list, i am a String);System.out.println(list.toString());}}4、一个ArrayList对象aList中存有若干个字符串元素，现欲遍历该ArrayList对象，删除其中所有值为abc的字符串元素，请用代码实现。publicclass test4 {publicstaticvoid main(String[] args) {ArrayListString aList = newArrayListString();aList.add(abc);aList.add(nihaoa);aList.add(nihaoa);aList.add(abc);aList.add(cdb);aList.add(abc);aList.add(cdb);System.out.println(aList.toString());IteratorString it = aList.iterator();while(it.hasNext()){String str = it.next();if(str.equals(abc)){it.remove();}}System.out.println(aList.toString());}}5、编写一个类，增加一个实例方法用于打印一条字符串。并使用反射手段创建该类的对象，并调用该对象中的方法。publicclass test5 {publicstaticvoid main(String[] args)throws Exception {ClassmyClass clazz = myClass.class;Method method = clazz.getMethod(printStr, String.class);method.invoke(clazz.newInst