自定义java泛型

自定义泛型：泛型接口，泛型实现类，泛型方法

泛型接口

package genericity;

public interface Box<E> {
	
	public void add(E e);
	public E get(int i);

}
           

泛型实现类

package genericity;

public class BoxImp<E> implements Box<E>{

	Object[] arr=new Object[10];
	int i=0;
	@Override
	public void add(E e) {
		arr[i]=e;
		i++;
	}

	@Override
	public E get(int i) {
		return (E)arr[i];
	}

}
           

测试

package genericity;

public class Test {
	
	public static void main(String[] args) {
		Box<String> box=new BoxImp<String>();
		box.add("hello");
		box.add("world");
		System.out.println(box.get(0)+box.get(1));
	}
}
           

类型限制<E extends Class>

接口

package genericity;

public interface Box<E extends Animal> {
	
	public void add(E e);
	public E get(int i);

}
           

实现类 

package genericity;

public class BoxImp<E extends Animal> implements Box<E>{

	Object[] arr=new Object[10];
	int i=0;
	@Override
	public void add(E e) {
		arr[i]=e;
		i++;
	}

	@Override
	public E get(int i) {
		return (E)arr[i];
	}

}
           

测试

package genericity;

public class Test {
	
	public static void main(String[] args) {
		Box<Dog> box=new BoxImp<Dog>();
		Dog d1=new Dog();
		box.add(d1);
	}
}
           

package genericity;

public interface Animal {
	public void play();
}
           

package genericity;

public class Dog implements Animal{
	public String name;
	@Override
	public void play() {
		// TODO Auto-generated method stub
		
	}
}
           

最后，泛型看上去好像是很多种类型，其实在内存中只是一种，只不过是为了提供编译时类型检查，以防止出现运行时异常