import java.util.ArrayList; /** * @authur zhangqizky * @apiNote 泛型模板:实现编写一次,万能匹配,又通过编译器保证类型安全:这就是泛型 */ public class Tamplate { public static void main(String[]args) { ArrayList<String> strList = new ArrayList<String>(); ArrayList<Float> floatList = new ArrayList<Float>(); strList.add("Hello"); String s = strList.get(0); //编译报错 // strList.add(new Integer(123)); //编译报错 // Integer n = strList.get(0); //标准库中ArrayList<T>实现了List<T>接口,它可以向上转型为List<T>。即public class ArrayList<T> implements List<T> { //... //} List<Integer> list = new ArrayList<Integer>(); //但是不能把ArrayList<Integer>向上转型为ArrayList<Number>或List<Number> } }
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