Java CopyOnWriteArrayList set()方法及实例

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参数提供的元素。该方法返回被新元素替换的元素。

语法：

public E set(int index, E element)

参数： 该方法需要以下两个参数：

• index ：包含新元素取代现有元素的位置。它是必须添加的。
• element ：包含要被替换的新元素。

返回值： 该方法返回被替换的 元素 。

异常： 当该方法的索引小于0或大于列表的大小时，会抛出 IndexOutOfBoundsException 。

下面是一些程序来说明CopyOnWriteArrayList.set()方法的使用：

程序1：

// 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<String> arrayList
            = new CopyOnWriteArrayList<String>();
 
        // 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);
    }
}

程序2：

// Program to illustrate the ArrayIndexOutOfBoundsException
 
import java.util.concurrent.CopyOnWriteArrayList;
 
public class CopyOnWriteArrayListDemo {
    public static void main(String[] args)
    {
 
        // creating an ArrayList
        CopyOnWriteArrayList<String> arrayList
            = new CopyOnWriteArrayList<String>();
 
        // 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);
        }
    }
}