遍歷刪除List中的元素有很多種方法，當運用不當的時候就會產生問題。下面主要看看以下幾種遍歷刪除List中元素的形式：

1.通過增強的for循環刪除符合條件的多個元素

2.通過增強的for循環刪除符合條件的一個元素

3.通過普通的for刪除刪除符合條件的多個元素

4.通過Iterator進行遍歷刪除符合條件的多個元素

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?

Java代碼??

/**?

?*?使用增強的for循環?

?*?在循環過程中從List中刪除元素以后，繼續循環List時會報ConcurrentModificationException?

?*/??

public?void?listRemove()?{??

????List<Student>?students?=?this.getStudents();??

????for?(Student?stu?:?students)?{??

????????if?(stu.getId()?==?2)???

????????????students.remove(stu);??

????}??

}??

?

?

Java代碼??

/**?

?*?像這種使用增強的for循環對List進行遍歷刪除，但刪除之后馬上就跳出的也不會出現異常?

?*/??

public?void?listRemoveBreak()?{??

????List<Student>?students?=?this.getStudents();??

????for?(Student?stu?:?students)?{??

????????if?(stu.getId()?==?2)?{??

????????????students.remove(stu);??

????????????break;??

????????}??

????}??

}??

?

?

Java代碼??

/**?

?*?這種遍歷有可能會遺漏某個元素,因為刪除元素后List的size在?

?*?變化，元素的索引也在變化，比如你循環到第2個元素的時候你把它刪了，?

?*?接下來你去訪問第3個元素，實際上訪問到的是原先的第4個元素。當訪問的元素?

?*?索引超過了當前的List的size后還會出現數組越界的異常，當然這里不會出現這種異常，?

?*?因為這里每遍歷一次都重新拿了一次當前List的size。?

?*/??

public?void?listRemove2()?{??

????List<Student>?students?=?this.getStudents();??

????for?(int?i=0;?i<students.size();?i++)?{??

????????if?(students.get(i).getId()%3?==?0)?{??

????????????Student?student?=?students.get(i);??

????????????students.remove(student);??

????????}??

????}??

}??

?

?

Java代碼??

/**?

?*?使用Iterator的方式也可以順利刪除和遍歷?

?*/??

public?void?iteratorRemove()?{??

????List<Student>?students?=?this.getStudents();??

????System.out.println(students);??

????Iterator<Student>?stuIter?=?students.iterator();??

????while?(stuIter.hasNext())?{??

????????Student?student?=?stuIter.next();??

????????if?(student.getId()?%?2?==?0)??

????????????stuIter.remove();//這里要使用Iterator的remove方法移除當前對象，如果使用List的remove方法，則同樣會出現ConcurrentModificationException??

????}??

????System.out.println(students);??

}??

?

?

附完整代碼如下：

?

Java代碼??

import?java.util.ArrayList;??

import?java.util.Iterator;??

import?java.util.List;??

??

public?class?ListRemove?{??

??

????public?static?void?main(String?args[])?{??

????????ListRemove?lr?=?new?ListRemove();??

????????lr.listRemove();??

????????lr.listRemoveBreak();??

//??????lr.listRemove2();??

//??????lr.iteratorRemove();??

????}??

??

????/**?

?????*?使用增強的for循環?

?????*?在循環過程中從List中刪除元素以后，繼續循環List時會報ConcurrentModificationException?

?????*/??

????public?void?listRemove()?{??

????????List<Student>?students?=?this.getStudents();??

????????for?(Student?stu?:?students)?{??

????????????if?(stu.getId()?==?2)???

????????????????students.remove(stu);??

????????}??

????}??

??????

????/**?

?????*?像這種使用增強的for循環對List進行遍歷刪除，但刪除之后馬上就跳出的也不會出現異常?

?????*/??

????public?void?listRemoveBreak()?{??

????????List<Student>?students?=?this.getStudents();??

????????for?(Student?stu?:?students)?{??

????????????if?(stu.getId()?==?2)?{??

????????????????students.remove(stu);??

????????????????break;??

????????????}??

????????}??

????}??

??????

????/**?

?????*?這種不使用增強的for循環，每次重新獲取list的size遍歷的情況運行時不會報錯，但是可能刪除的結果是錯的。?

?????*/??

????public?void?listRemove2()?{??

????????List<Student>?students?=?this.getStudents();??

????????for?(int?i=0;?i<students.size();?i++)?{??

????????????if?(students.get(i).getId()%2?==?0)??

????????????????students.remove(i);??

????????}??

????}??

??????

????/**?

?????*?使用Iterator的方式也可以順利刪除和遍歷?

?????*/??

????public?void?iteratorRemove()?{??

????????List<Student>?students?=?this.getStudents();??

????????System.out.println(students);??

????????Iterator<Student>?stuIter?=?students.iterator();??

????????while?(stuIter.hasNext())?{??

????????????Student?student?=?stuIter.next();??

????????????if?(student.getId()?%?2?==?0)??

????????????????stuIter.remove();??

????????}??

????????System.out.println(students);??

????}??

??????

????private?List<Student>?getStudents()?{??

????????List<Student>?students?=?new?ArrayList<Student>()?{??

????????????{??

????????????????int?i?=?0;??

????????????????while?(i++?<?10)?{??

????????????????????Student?student?=?new?Student(i,?"201200"?+?i,?"name_"?+?i);??

????????????????????this.add(student);??

????????????????}??

????????????}??

????????};??

????????return?students;??

????}??

}??

?

?

Java代碼??

public?class?Student?{??

??

????private?int?id;??

????private?String?stuNo;??

????private?String?name;??

??????

????public?Student()?{??

??????????

????}??

??????

????public?Student(int?id,?String?stuNo,?String?name)?{??

????????this.id?=?id;??

????????this.stuNo?=?stuNo;??

????????this.name?=?name;??

????}??

??

????public?int?getId()?{??

????????return?id;??

????}??

??

????public?void?setId(int?id)?{??

????????this.id?=?id;??

????}??

??

????public?String?getStuNo()?{??

????????return?stuNo;??

????}??

??

????public?void?setStuNo(String?stuNo)?{??

????????this.stuNo?=?stuNo;??

????}??

??

????public?String?getName()?{??

????????return?name;??

????}??

??

????public?void?setName(String?name)?{??

????????this.name?=?name;??

????}??

??

????@Override??

????public?String?toString()?{??

????????return?"Student?[id="?+?id?+?",?name="?+?name?+?",?stuNo="?+?stuNo??

????????????????+?"]";??

????}??

??????

}

from:?http://elim.iteye.com/blog/1523785

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