Java中的 CopyOnWriteArrayList listIterator() 方法

CopyOnWriteArrayList的listIterator()方法以正确的顺序在此列表中的元素上返回一个 listIterator。 listIterator 不支持 remove、set 或 add 方法。

句法：

public ListIterator listIterator()

参数：该函数不接受任何参数。

返回值：该函数返回此列表中元素的列表迭代器（以正确的顺序）

下面的程序说明了上述函数：

方案一：

Java

// Java Program to illustrate the CopyOnWriteArrayList
// listIterator() method in Java
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;
 
public class GFG {
    public static void main(String[] args)
    {
 
        // create object of CopyOnWriteArrayList
        CopyOnWriteArrayList ArrLis
            = new CopyOnWriteArrayList();
 
        // Add elements
        ArrLis.add(32);
        ArrLis.add(67);
        ArrLis.add(67);
        ArrLis.add(100);
 
        // print CopyOnWriteArrayList
        System.out.println("CopyOnWriteArrayList: " + ArrLis);
 
        // Call listIterator() method of
        Iterator iteratorVals = ArrLis.listIterator();
 
        // Print elements of iterator
        // created from CopyOnWriteArrayList
        System.out.println("The iterator values"
                           + " of CopyOnWriteArrayList are:");
 
        // prints the elements using an iterator
        while (iteratorVals.hasNext()) {
            System.out.println(iteratorVals.next());
        }
    }
}

输出：

CopyOnWriteArrayList: [32, 67, 67, 100]
The iterator values of CopyOnWriteArrayList are:
32
67
67
100

CopyOnWriteArrayList的listIterator(index)方法从特定索引开始以适当的顺序在此列表中的元素上返回一个 listIterator。 listIterator 不支持 remove、set 或 add 方法。

句法：

public ListIterator listIterator(int index)

参数：该函数接受一个参数索引，它指定要从列表迭代器返回的第一个元素的索引。

返回值：该函数从指定索引开始（以正确的顺序）返回此列表中元素的列表迭代器。

异常：如果索引超出范围，该函数将抛出IndexOutOfBoundsException 。

下面的程序说明了上述函数：

方案一：

Java

// Java Program to illustrate the CopyOnWriteArrayList
// listIterator() method in Java
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;
 
public class GFG {
    public static void main(String[] args)
    {
 
        // create object of CopyOnWriteArrayList
        CopyOnWriteArrayList ArrLis
            = new CopyOnWriteArrayList();
 
        // Add elements
        ArrLis.add("gopal");
        ArrLis.add("gfg");
        ArrLis.add("jgec");
        ArrLis.add("sudo");
 
        // print CopyOnWriteArrayList
        System.out.println("CopyOnWriteArrayList: " + ArrLis);
 
        // Call listIterator() method from 2nd index
        Iterator iteratorVals = ArrLis.listIterator(2);
 
        // Print elements of iterator
        // created from CopyOnWriteArrayList
        System.out.println("The iterator values"
                           + " of CopyOnWriteArrayList are:");
 
        // prints the elements using an iterator
        while (iteratorVals.hasNext()) {
            System.out.println(iteratorVals.next());
        }
    }
}

输出：

CopyOnWriteArrayList: [gopal, gfg, jgec, sudo]
The iterator values of CopyOnWriteArrayList are:
jgec
sudo

方案二：

Java

// Java Program to illustrate the CopyOnWriteArrayList
// listIterator() method in Java, exception
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;
 
public class GFG {
    public static void main(String[] args)
    {
 
        // create object of CopyOnWriteArrayList
        CopyOnWriteArrayList ArrLis
            = new CopyOnWriteArrayList();
 
        // Add elements
        ArrLis.add("gopal");
        ArrLis.add("gfg");
        ArrLis.add("jgec");
        ArrLis.add("sudo");
 
        // print CopyOnWriteArrayList
        System.out.println("CopyOnWriteArrayList: " + ArrLis);
 
        // Call listIterator() method from 6th index
        // hence exception is returned
        Iterator iteratorVals = ArrLis.listIterator(6);
 
        // Print elements of iterator
        // created from CopyOnWriteArrayList
        System.out.println("The iterator values"
                           + " of CopyOnWriteArrayList are:");
 
        // prints the elements using an iterator
        while (iteratorVals.hasNext()) {
            System.out.println(iteratorVals.next());
        }
    }
}

输出：

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 6
    at java.util.concurrent.CopyOnWriteArrayList.listIterator(CopyOnWriteArrayList.java:1107)
    at GFG.main(GFG.java:25)

参考： https: Java/util/concurrent/CopyOnWriteArrayList.html#listIterator–