1. public class Test {
2. public <T extends Comparable> T findLarger(T x, T y) {
3. if(x.compareTo(y) > 0) {
4. return x;
5. } else {
6. return y;
7. }
8. }
9. }
and:
22. Test t = new Test();
23. // insert code here
Which two will compile without errors when inserted at line 23?
(Choose two.)
A. Object x = t.findLarger(123, “456”);
B. int x = t.findLarger(123, new Double(456));
C. int x = t.findLarger(123, new Integer(456));
D. int x = (int) t.findLarger(new Double(123), new Double(456));

1.       public class Test {
2. public <T extends Comparable> T findLarger(T x, T y) { //泛型方法
3. if(x.compareTo(y) > 0) {
4. return x;
5. } else {
6. return y;
7. }
8. }
9. }
and:
22. Test t = new Test();
23. // insert code here
Which two will compile without errors when inserted at line 23?
(Choose two.)

2.     这题考察的是泛型方法中参数类型的推断知识

3.       Object x = t.findLarger(123, "456");//编译无错 ，123 “456”的最大交集是Object

4.          int x =(int) t.findLarger(new Double(123), new Double(456));//编译错误，不能从 Double 强制类型转换为 int

5.             int x = t.findLarger(123, new Integer(456));//正常 int 和Integer之间可以拆箱装箱

6.              int x = t.findLarger(123, new Double(456));//编译错误，类型不匹配：不能从 Number&Comparable<?> 转换为 int

7.       具体可看张老师的ppt截图

选择 CD 两项  得保证参数传入的类型一致。

1.                  int x = findLarger(123, new Double(456));//123可以装箱为Integer，跟后面的Double的共同父类是Number，所以会返回Number类型，用int型来接受，就会报错
   
2.                  int u = findLarger(123, new Integer(456));//两者都是Integer型，返回的也是Intger，自动拆箱，所以不会报错
   
3.                  int y = (int)findLarger(new Double(123), new Double(456));//Double跟Double，返回的也会是Double类型，想直接强转为int型，会报错

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