List中泛型的使用_JAVA_编程开发_程序员俱乐部

import java.util.ArrayList;

class Apple {
	private static long counter;
	private final long id = counter++;

	public long id() {
		return id;
	}
}

class Orange {
}

/**
 * 
 * 此处未使用泛型，当试图将orange对象转型为apple是，你就会得到一个语法错误；
 * @author hong.su
 *
 */
//public class AppleandOrangeWithoutGenerics {
//	@SuppressWarnings("unchecked")
//	public static void main(String[] args){
//		ArrayList apple = new ArrayList();
//		for (int i = 0; i < 3; i++) {
//			apple.add(new Apple());
//			apple.add(new Orange());
//			for (int j = 0; j < apple.size(); j++) {
//				((Apple)apple.get(i)).id();
//			}
//		}
//	}
//}

public class AppleandOrangeWithoutGenerics{
	@SuppressWarnings("unchecked")
	public static void main(String[] args){
		ArrayList<Apple> apples = new ArrayList<Apple>();
		for (int i = 0; i < 3; i++) {
			apples.add(new Apple());
			for (int j = 0; j < apples.size(); j++) {
				System.out.println(apples.get(j).id());
				for (Apple c : apples) {
					System.out.println(c.id());
				}
			}
		}
	}
	
}