java_泛型方法使用实例

//提供两种使用情况，第二种情况定义前者是后者的子类-类型通配方式

 

package ming;

import java.util.ArrayList;

import java.util.Collection;



public class GenericMethodTest {



	static <T> void fromArraytoCollection(T[] a, Collection<T> c) {

		for (T o : a) {

			c.add(o);

		}

	}



	public static void main(String[] args) {

		// TODO Auto-generated method stub

		//T stand for Object

		Object[] oa = new Object[100];

		Collection<Object> co = new ArrayList<Object>();

		fromArraytoCollection(oa,co);

		

		//T stand for Number

		Integer[] ia = new Integer[100];

		Float[] fa = new Float[100];

		Collection<Number> cn = new ArrayList<Number>();

		

		fromArraytoCollection(ia,cn);

		fromArraytoCollection(fa,cn);

		

		

	}



}

 

package ming;



import java.util.ArrayList;

import java.util.Collection;

import java.util.List;



public class GenericMethodTest {



	static <T> void fromArraytoCollection(Collection<? extends T> from,

			Collection<T> to) {

		for (T ele : from) {

			to.add(ele);

		}

	}



	public static void main(String[] args) {

		List<Object> ao = new ArrayList<Object>();

		List<String> as = new ArrayList<String>();

		// string is subclass of object

		fromArraytoCollection(as, ao);



	}



}