前提:
使用迭代器删除List中的元素,发现删除时报错。
代码:
List<String> list = Arrays.asList("aaa","aaab","ccc","ccca","efgr");
Iterator<String> iterator = list.iterator();
while (iterator.hasNext()){
String s = iterator.next();
if(s.contains("a")){
iterator.remove();
}
System.out.println("delete前"+s);
}
System.out.println("delete后"+list1);
}
错误:ava.lang.UnsupportedOperationException
at java.util.AbstractList.remove(AbstractList.java:161)
at java.util.AbstractList$Itr.remove(AbstractList.java:374)
at com.example.demo.service.TestService.test10(TestService.java:180)
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 org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:119)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)
原因:
asList返回的是Arrays下的ArrayList 并不是Util下的ArrayList 没有实现romove的方法 因此不能使用迭代器去删除
修改:
//asList返回的是Arrays下的ArrayList 并不是Util下的ArrayList 没有实现romove的方法 因此不能使用迭代器去删除
List<String> list = Arrays.asList("aaa","aaab","ccc","ccca","efgr");
//将返回的list重新包装
List<String> list1 = new ArrayList<>(list);
Iterator<String> iterator = list1.iterator();
while (iterator.hasNext()){
String s = iterator.next();
if(s.contains("a")){
iterator.remove();
}
System.out.println("delete前"+s);
}
System.out.println("delete后"+list1);
结果:
delete前aaa
delete前aaab
delete前ccc
delete前ccca
delete前efgr
delete后[ccc, efgr]