java中的subList

package test;
import java.util.ArrayList;
import java.util.List;

 //对parentList进行结构性修改，访问subList会抛出异常

public class TestSubList {
    public static void main(String[] args) {
        List<String> parentList = new ArrayList<String>();
        for(int i = 0;i<10;i++) {
            parentList.add(String.valueOf(i));
        }
        List<String> subList = parentList.subList(0,3);
        System.out.println(subList);
        subList.clear();
        parentList.add("undef");
        System.out.println(subList);
    }
}
这段代码会抛出异常：

Exception in thread "main" java.util.ConcurrentModificationException

at java.util.ArrayList$SubList.checkForComodification(ArrayList.java:1231)

at java.util.ArrayList$SubList.listIterator(ArrayList.java:1091)

at java.util.AbstractList.listIterator(AbstractList.java:299)

at java.util.ArrayList$SubList.iterator(ArrayList.java:1087)

at java.util.AbstractCollection.toString(AbstractCollection.java:454)

at java.lang.String.valueOf(String.java:2994)

at java.io.PrintStream.println(PrintStream.java:821)

at test.TestSubList.main(TestSubList.java:21)

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:147)

Process finished with exit code 1