实例化后的list的默认值

Posted 2020-10-23 kangkaii

public class List默认值 {
    public static void main(String[] args) {
        List<String> arrayList = new ArrayList<>();
        List<String> linkedList = new LinkedList<>();
        if (arrayList.isEmpty()) {
            System.out.println("arrayList默认是空");
        }
        if (linkedList.isEmpty()) {
            System.out.println("linkedList默认是空");
        }
        if (arrayList != null) {
            System.out.println("arrayList默认不是null");
        }
        if (linkedList != null) {
            System.out.println("linkedList默认不是null");
        }
        if (arrayList.size() == 0) {
            System.out.println("arrayList.size()是0");
        }
        if (linkedList.size() == 0) {
            System.out.println("linkedList.size()是0");
        }
        try {
            System.out.println(arrayList.get(0)+"arrayList.get(0)没抛异常");
        }catch (Exception e){
            System.out.println(arrayList.get(0)+"arrayList.get(0)抛了异常");
        }
        try {
            System.out.println(linkedList.get(0)+"linkedList.get(0)没抛异常");
        }catch (Exception e){
            System.out.println(linkedList.get(0)+"linkedList.get(0)抛了异常");
        }
    }
}

结果为：

arrayList默认是空
linkedList默认是空
arrayList默认不是null
linkedList默认不是null
arrayList.size()是0
linkedList.size()是0
arrayList.get(0)抛了异常
linkedList.get(0)抛了异常