Java笔记-集合

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实例化后的list的默认值

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nulllinkedList默认不是nullarrayList.size()是0linkedList.size()是0Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0at java.util.ArrayList.rangeCheck(ArrayList.java:653)at java.util.ArrayList.get(ArrayList.java:429)at test.test.List结构.List默认值.main(List默认值.java:35)

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