總結遍歷List時刪除元素

遍歷List時候發現問題，查看了別人寫的發現還可以有另外一種解決方法。

http://blog.csdn.net/dongzhouzhou/article/details/15378433

這個鏈接是別人總結的遍歷刪除List元素的方法，

在這裏增加了一種方法每次遍歷都重新實例一個ArraryList就可以了

因爲增加for循環使用迭代器的方法

public E next() {
        checkForComodification();
        try {
                E next = get(cursor);
                lastRet = cursor++;
                return next;
        } catch (IndexOutOfBoundsException e) {
                checkForComodification();
                throw new NoSuchElementException();
        }
}


final void checkForComodification() {
        if (modCount != expectedModCount)
                throw new ConcurrentModificationException();
        }
}

modCount != expectedModCount 保證了迭代器自從創建到遍歷的過程中，集合沒有被修改，如果被修改了就會報出這個異常

下面根據這個問題解決方法就是每次迭代都重新實例一下ArrayList，這樣增刪元素就不會有影響了

import java.util.ArrayList;
import java.util.List;

public class listRemoveValid {
	
	class Student {
		private int id;
		public Student(int id){this.id=id;}
		public int getId() {
			return id;
		}
		public void setId(int id) {
			this.id = id;
		}
	}
	
	public void listRemove() {    
	    List<Student> students = this.getStudents();    
	    for (Student stu : new ArrayList<Student>(students)) {  
	    	System.out.println(stu.id);
	        if (stu.getId() == 2)     
	            students.remove(stu);
	    } 
	    
	    System.out.println("刪除後數量:"+students.size());
	    
	}    
	
	private List<Student> getStudents() {
		List<Student> students = new ArrayList<Student>();
		students.add(new Student(1));
		students.add(new Student(2));
		students.add(new Student(3));
		students.add(new Student(4));
		students.add(new Student(5));
		return students;
	}

	public static void main(String[] args) {
		new listRemoveValid().listRemove();
	}

}