Java中的 CopyOnWriteArrayList set() 方法及示例

CopyOnWriteArrayList 类中的set(E e)方法将指定索引处的元素替换为作为该方法的参数提供的元素。该方法返回已被新元素替换的元素。
句法：

public E set(int index, E element)

参数：该方法采用下面提到的两个参数：

• 索引：包含新元素替换现有元素的位置。必须添加。
• Element ：包含要替换的新元素。

返回值：该方法返回已被替换的元素。
异常：当方法的索引小于 0 或大于列表大小时，方法会抛出IndexOutOfBoundsException 。
下面是一些程序来说明 CopyOnWriteArrayList.set() 方法的使用：
方案一：

Java

// Program to illustrate the use of set() method
 
import java.util.concurrent.CopyOnWriteArrayList;
 
public class CopyOnWriteArrayListDemo {
    public static void main(String[] args)
    {
 
        // creating an ArrayList
        CopyOnWriteArrayList arrayList
            = new CopyOnWriteArrayList();
 
        // Adding elements to the list
        arrayList.add(0, "geeks");
        arrayList.add(1, "for");
        arrayList.add(2, "geeksforgeeks");
 
        // before invoking the set() method
        System.out.println("CopyOnWriteArrayList: "
                           + arrayList);
 
        // invoking the set() method
        String returnValue
            = arrayList.set(0, "toodles");
 
        // printing the returned value
        System.out.println("The value returned "
                           + "on calling set() method:"
                           + returnValue);
 
        // print CopyOnWriteArrayList
        System.out.println("CopyOnWriteArrayList "
                           + "after calling set():"
                           + arrayList);
    }
}

方案二：

Java

// Program to illustrate the ArrayIndexOutOfBoundsException
 
import java.util.concurrent.CopyOnWriteArrayList;
 
public class CopyOnWriteArrayListDemo {
    public static void main(String[] args)
    {
 
        // creating an ArrayList
        CopyOnWriteArrayList arrayList
            = new CopyOnWriteArrayList();
 
        // Adding elements to the list
        arrayList.add(0, "geeks");
        arrayList.add(1, "for");
        arrayList.add(2, "geeksforgeeks");
 
        // before invoking the set() method
        System.out.println("CopyOnWriteArrayList: "
                           + arrayList);
 
        try {
 
            System.out.println("Trying to add "
                               + "element at index 4 "
                               + "using set() method");
 
            // invoking the set() method
            String returnValue
                = arrayList.set(4, "toodles");
            // printing the returned value
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}