Java知多少（41）泛型详解

1 x = 10、y = 10
2 x = 12.88、y = 129.65
3 x = "东京180度"、y = "北纬210度"

1 int --> Integer --> Object
2 double -->Double --> Object
3 String --> Object

 1 public class Demo {
 2     public static void main(String[] args){
 3         Point p = new Point();
 4         p.setX(10);  // int -> Integer -> Object
 5         p.setY(20);
 6         int x = (Integer)p.getX();  // 必须向下转型
 7         int y = (Integer)p.getY();
 8         System.out.println("This point is：" + x + ", " + y);
 9        
10         p.setX(25.4);  // double -> Integer -> Object
11         p.setY("东京180度");
12         double m = (Double)p.getX();  // 必须向下转型
13         double n = (Double)p.getY();  // 运行期间抛出异常
14         System.out.println("This point is：" + m + ", " + n);
15     }
16 }
17 class Point{
18     Object x = 0;
19     Object y = 0;
20     public Object getX() {
21         return x;
22     }
23     public void setX(Object x) {
24         this.x = x;
25     }
26     public Object getY() {
27         return y;
28     }
29     public void setY(Object y) {
30         this.y = y;
31     }
32 }

 1 public class Demo {
 2     public static void main(String[] args){
 3         // 实例化泛型类
 4         Point<Integer, Integer> p1 = new Point<Integer, Integer>();
 5         p1.setX(10);
 6         p1.setY(20);
 7         int x = p1.getX();
 8         int y = p1.getY();
 9         System.out.println("This point is：" + x + ", " + y);
10        
11         Point<Double, String> p2 = new Point<Double, String>();
12         p2.setX(25.4);
13         p2.setY("东京180度");
14         double m = p2.getX();
15         String n = p2.getY();
16         System.out.println("This point is：" + m + ", " + n);
17     }
18 }
19 // 定义泛型类
20 class Point<T1, T2>{
21     T1 x;
22     T2 y;
23     public T1 getX() {
24         return x;
25     }
26     public void setX(T1 x) {
27         this.x = x;
28     }
29     public T2 getY() {
30         return y;
31     }
32     public void setY(T2 y) {
33         this.y = y;
34     }
35 }

 1 public class Demo {
 2     public static void main(String[] args){
 3         // 实例化泛型类
 4         Point<Integer, Integer> p1 = new Point<Integer, Integer>();
 5         p1.setX(10);
 6         p1.setY(20);
 7         p1.printPoint(p1.getX(), p1.getY());
 8        
 9         Point<Double, String> p2 = new Point<Double, String>();
10         p2.setX(25.4);
11         p2.setY("东京180度");
12         p2.printPoint(p2.getX(), p2.getY());
13     }
14 }
15 // 定义泛型类
16 class Point<T1, T2>{
17     T1 x;
18     T2 y;
19     public T1 getX() {
20         return x;
21     }
22     public void setX(T1 x) {
23         this.x = x;
24     }
25     public T2 getY() {
26         return y;
27     }
28     public void setY(T2 y) {
29         this.y = y;
30     }
31    
32     // 定义泛型方法
33     public <T1, T2> void printPoint(T1 x, T2 y){
34         T1 m = x;
35         T2 n = y;
36         System.out.println("This point is：" + m + ", " + n);
37     }
38 }

1 public static <V1, V2> void printPoint(V1 x, V2 y){
2     V1 m = x;
3     V2 n = y;
4     System.out.println("This point is：" + m + ", " + n);
5 }

 1 public class Demo {
 2     public static void main(String arsg[]) {
 3         Info<String> obj = new InfoImp<String>("www.weixueyuan.net");
 4         System.out.println("Length Of String: " + obj.getVar().length());
 5     }
 6 }
 7 //定义泛型接口
 8 interface Info<T> {
 9     public T getVar();
10 }
11 //实现接口
12 class InfoImp<T> implements Info<T> {
13     private T var;
14     // 定义泛型构造方法
15     public InfoImp(T var) {
16         this.setVar(var);
17     }
18     public void setVar(T var) {
19         this.var = var;
20     }
21     public T getVar() {
22         return this.var;
23     }
24 }