Arrays.asList引起的java.lang.UnsupportedOperationException解决方法

在项目中对List进行操作时报错java.lang.UnsupportedOperationException,后来发现操作的List是由数组转换而成的,通过看源码发现问题,并写测试程序如下。 
代码块:

public class ListTest {
    public static void main(String[] args) {
        String[] array = {"1","2","3","4","5"};
        List<String> list = Arrays.asList(array);
        list.add("6");
    }
}

执行结果:

Exception in thread "main" java.lang.UnsupportedOperationException
    at java.util.AbstractList.add(AbstractList.java:148)
    at java.util.AbstractList.add(AbstractList.java:108)
    at com.atguigu.test.ListTest.main(ListTest.java:11)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

发生问题的原因如下: 
调用Arrays.asList()生产的List的add、remove方法时报异常,这是由Arrays.asList() 返回的市Arrays的内部类ArrayList, 而不是java.util.ArrayList。Arrays的内部类ArrayList和java.util.ArrayList都是继承AbstractList,remove、add等方法AbstractList中是默认throw UnsupportedOperationException而且不作任何操作。java.util.ArrayList重新了这些方法而Arrays的内部类ArrayList没有重新,所以会抛出异常。解决方法如下:

public class ListTest {
    public static void main(String[] args) {
        String[] array = {"1","2","3","4","5"};
        List<String> list = Arrays.asList(array);
        List arrList = new ArrayList(list);
        arrList.add("6");
    }
}

 

posted @ 2018-05-27 13:33  夏威夷8080  阅读(206)  评论(0编辑  收藏  举报