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

public class Demo {
  public static void main(String[] args){
    Point p = new Point();
    p.setX(10); // int -> Integer -> Object
    p.setY(20);
    int x = (Integer)p.getX(); // 必须向下转型
    int y = (Integer)p.getY();
    System.out.println("This point is：" + x + ", " + y);
    
    p.setX(25.4); // double -> Integer -> Object
    p.setY("东京180度");
    double m = (Double)p.getX(); // 必须向下转型
    double n = (Double)p.getY(); // 运行期间抛出异常
    System.out.println("This point is：" + m + ", " + n);
  }
}
class Point{
  Object x = 0;
  Object y = 0;
  public Object getX() {
    return x;
  }
  public void setX(Object x) {
    this.x = x;
  }
  public Object getY() {
    return y;
  }
  public void setY(Object y) {
    this.y = y;
  }
}

public class Demo {
  public static void main(String[] args){
    // 实例化泛型类
    Point<Integer, Integer> p1 = new Point<Integer, Integer>();
    p1.setX(10);
    p1.setY(20);
    int x = p1.getX();
    int y = p1.getY();
    System.out.println("This point is：" + x + ", " + y);
    
    Point<Double, String> p2 = new Point<Double, String>();
    p2.setX(25.4);
    p2.setY("东京180度");
    double m = p2.getX();
    String n = p2.getY();
    System.out.println("This point is：" + m + ", " + n);
  }
}
// 定义泛型类
class Point<T1, T2>{
  T1 x;
  T2 y;
  public T1 getX() {
    return x;
  }
  public void setX(T1 x) {
    this.x = x;
  }
  public T2 getY() {
    return y;
  }
  public void setY(T2 y) {
    this.y = y;
  }
}

This point is：10, 20
This point is：25.4, 东京180度

  className variable<dataType1, dataType2> = new className<dataType1, dataType2>();

  className variable<dataType1, dataType2> = new className();

public class Demo {
  public static void main(String[] args){
    // 实例化泛型类
    Point<Integer, Integer> p1 = new Point<Integer, Integer>();
    p1.setX(10);
    p1.setY(20);
    p1.printPoint(p1.getX(), p1.getY());
    
    Point<Double, String> p2 = new Point<Double, String>();
    p2.setX(25.4);
    p2.setY("东京180度");
    p2.printPoint(p2.getX(), p2.getY());
  }
}
// 定义泛型类
class Point<T1, T2>{
  T1 x;
  T2 y;
  public T1 getX() {
    return x;
  }
  public void setX(T1 x) {
    this.x = x;
  }
  public T2 getY() {
    return y;
  }
  public void setY(T2 y) {
    this.y = y;
  }
  
  // 定义泛型方法
  public <T1, T2> void printPoint(T1 x, T2 y){
    T1 m = x;
    T2 n = y;
    System.out.println("This point is：" + m + ", " + n);
  }
}

This point is：10, 20
This point is：25.4, 东京180度

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

public class Demo {
  public static void main(String arsg[]) {
    Info<String> obj = new InfoImp<String>("www.weixueyuan.net");
    System.out.println("Length Of String: " + obj.getVar().length());
  }
}
//定义泛型接口
interface Info<T> {
  public T getVar();
}
//实现接口
class InfoImp<T> implements Info<T> {
  private T var;
  // 定义泛型构造方法
  public InfoImp(T var) {
    this.setVar(var);
  }
  public void setVar(T var) {
    this.var = var;
  }
  public T getVar() {
    return this.var;
  }
}

Length Of String: 18

public class Demo {
  public static void main(String[] args){
    Point p = new Point(); // 类型擦除
    p.setX(10);
    p.setY(20.8);
    int x = (Integer)p.getX(); // 向下转型
    double y = (Double)p.getY();
    System.out.println("This point is：" + x + ", " + y);
  }
}
class Point<T1, T2>{
  T1 x;
  T2 y;
  public T1 getX() {
    return x;
  }
  public void setX(T1 x) {
    this.x = x;
  }
  public T2 getY() {
    return y;
  }
  public void setY(T2 y) {
    this.y = y;
  }
}

This point is：10, 20.8

public <T> T getMax(T array[]){
  T max = null;
  for(T element : array){
    max = element.doubleValue() > max.doubleValue() ? element : max;
  }
  return max;
}

public <T extends Number> T getMax(T array[]){
  T max = null;
  for(T element : array){
    max = element.doubleValue() > max.doubleValue() ? element : max;
  }
  return max;
}

public <T> T getMax(T array[]){
  T max = null;
  for(T element : array){
    max = element.doubleValue() > max.doubleValue() ? element : max;
  }
  return max;
}

public <T extends Number> T getMax(T array[]){
  T max = null;
  for(T element : array){
    max = element.doubleValue() > max.doubleValue() ? element : max;
  }
  return max;
}