基于java中泛型的总结分析

//这是定义的坐标点类
class Point {
    private Object x;
    private Object y;

    //用Object来表示不确定的类型
    public Point(Object x, Object y) {
        this.setX(x);
        this.setY(y);
    }
    public void setX(Object x) {
        this.x = x;
    }
    public Object getX() {
        return x;
    }
    public void setY(Object y) {
        this.y = y;
    }
    public Object getY() {
        return y;
    }

}

//测试类
public class Demo {
    public static void main(String[] args) {
        System.out.println("用浮点数表示坐标: ");
        Point p = new Point(12.23,23.21);
        //这里把Object类转为Double类，然后自动拆箱，下面两种一样
        System.out.println("X的坐标 " + (Double)p.getX());
        System.out.println("Y的坐标 " + (Double)p.getY());
        System.out.println();

        System.out.println("用整数表示坐标: ");
        Point p2 = new Point(12, 23);
        System.out.println("X的坐标 " + (Integer)p2.getX());
        System.out.println("Y的坐标 " + (Integer)p2.getY());
        System.out.println();

        System.out.println("用字符串表示坐标: ");
        Point p3 = new Point("北纬29度", "东经113度");
        System.out.println("X的坐标 " + (String)p3.getX());
        System.out.println("Y的坐标 " + (String)p3.getY());
    }
}

class Point<T> {
    //这里用T来表示不确定的类型
    private T x;
    private T y;
    public Point(T x, T y) {
        this.setX(x);
        this.setY(y);
    }
    public T getX() {
        return x;
    }
    public void setX(T x) {
        this.x = x;
    }
    public T getY() {
        return y;
    }
    public void setY(T y) {
        this.y = y;
    }
}

public class Demo {
    public static void main(String[] args) {
        System.out.println("用浮点数表示坐标: ");
        //用泛型改写后，使用数据无需再做向下转型处理
        Point<Double> p = new Point<Double>(12.23,23.21);
        System.out.println("X的坐标 " + p.getX());
        System.out.println("Y的坐标 " + p.getY());
        System.out.println();

        System.out.println("用整数表示坐标: ");
        Point<Integer> p2 = new Point<Integer>(12, 23);
        System.out.println("X的坐标 " + p2.getX());
        System.out.println("Y的坐标 " + p2.getY());
        System.out.println();

        System.out.println("用字符串表示坐标: ");
        Point<String> p3 = new Point<String>("北纬29度", "东经113度");
        System.out.println("X的坐标 " + p3.getX());
        System.out.println("Y的坐标 " + p3.getY());
    }
}

//类名后面不再定义泛型
class Print {
    //在方法中定义泛型
    public <T> void print(T t) {
        System.out.println(t);
    }

    public <E> void show(E e) {
        System.out.println(e);
    }
}

public class Demo {
    public static void main(String[] args) {
        Print p = new Print();
        p.print(12);
        p.print("hello");
        p.show(new Integer(33));
        p.show(23);
    }
}

//定义一个泛型接口
interface Inter<T>
{
    public void print(T t);
}

//实现方式一：
class InterDemo1 implements Inter<String> {
    public void print(String t) {
        System.out.println("print: " + t);
    }
}

//实现方式二：
class InterDemo2<T> implements Inter<T> {
    public void print(T t) {
        System.out.println("print: " + t);
    }
}

class Demo {
    public static void main(String[] args) {
        InterDemo1 id1 = new InterDemo1();
        id1.print("hello");
        InterDemo2<Integer> id2 = new InterDemo2<Integer>();
        id2.print(new Integer(23));
    }
}