import java.util.*;
public class wren{ public static void main(String args[]){
List<String> li = new ArrayList<String>();
Random a = new Random();
Iterator it = li.iterator(); String s = new String();
int b = 0;
for(int i = 0;i<5;i++){
b= a.nextInt(10);
li.add(Integer.toString(b));
}
Collections.sort(li);
for(int i = 0; i<li.size();i++){
System.out.println(li.get(i));
}
System.out.println("---------------------");
Collections.reverse(li);
for(int i = 0; i<li.size();i++)
System.out.println(li.get(i));
while(it.hasNext()){
it.next(); //不加这句话就没有错误,为什么阿?
System.out.println(b);
b++;
}
}
}
出错了。。
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:3
72)
at java.util.AbstractList$Itr.next(AbstractList.java:343)
at wren.main(wren.java:29)
public class wren{ public static void main(String args[]){
List<String> li = new ArrayList<String>();
Random a = new Random();
Iterator it = li.iterator(); String s = new String();
int b = 0;
for(int i = 0;i<5;i++){
b= a.nextInt(10);
li.add(Integer.toString(b));
}
Collections.sort(li);
for(int i = 0; i<li.size();i++){
System.out.println(li.get(i));
}
System.out.println("---------------------");
Collections.reverse(li);
for(int i = 0; i<li.size();i++)
System.out.println(li.get(i));
while(it.hasNext()){
it.next(); //不加这句话就没有错误,为什么阿?
System.out.println(b);
b++;
}
}
}
出错了。。
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:3
72)
at java.util.AbstractList$Itr.next(AbstractList.java:343)
at wren.main(wren.java:29)
it.next(); //不加这句话就没有错误,为什么阿?
System.out.println(b);
b++;
}
while本来就是循环啊!
System.out.println(b);
b++;
}
it.hasNext() ; 应该会执行 it.next()的,如果你在while中改变了它 ,while会判断 ,就好如for里面一样吧
移到while循环上面来
你list都没准备好就放到迭代器中了Iterator it = li.iterator();
while (it.hasNext()) {
it.next(); // 不加这句话就没有错误,为什么阿?
System.out.println(b);
b++;
}
it.next(); //不加这句话就没有错误,为什么阿?
System.out.println(b);
b++;
}的上边
http://blog.sina.com.cn/s/blog_670eabd10100n7qa.html