Java CopyOnWriteArrayList get()方法

CopyOnWriteArrayList 的 get(index) 方法返回指定索引处的元素。

语法

public E get(int index)

参数： 该函数接受一个强制性参数index，该参数指定了要返回的元素的索引。

返回值： 该函数返回给定索引的元素。

异常： 如果索引超出范围，该函数会抛出IndexOutOfBoundsException。

下面的程序说明了上述函数。

程序1 :

// Java Program to illustrate the 
// CopyOnWriteArrayList get() 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<Integer> ArrLis
            = new CopyOnWriteArrayList<Integer>();
  
        // Add elements
        ArrLis.add(32);
        ArrLis.add(67);
        ArrLis.add(98);
        ArrLis.add(100);
  
        // print CopyOnWriteArrayList
        System.out.println("CopyOnWriteArrayList: " 
                                          + ArrLis);
  
        // 2nd index in the arraylist
        System.out.println("Element at 2nd index: " 
                                    + ArrLis.get(2));
    }
}

输出。

CopyOnWriteArrayList: [32, 67, 98, 100]
Element at 2nd index: 98

程序2

// Java Program to illustrate the 
// CopyOnWriteArrayList get() 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<String> ArrLis
            = new CopyOnWriteArrayList<String>();
  
        // Add elements
        ArrLis.add("gopal");
        ArrLis.add("gfg");
        ArrLis.add("jgec");
        ArrLis.add("sudo");
  
        // print CopyOnWriteArrayList
        System.out.println("CopyOnWriteArrayList: " 
                                          + ArrLis);
  
        // 4th index element of the arraylist
        // out of range, hence error
        System.out.println("CopyOnWriteArrayList: "
                                    + ArrLis.get(4));
    }
}

输出

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4
    at java.util.concurrent.CopyOnWriteArrayList.get(CopyOnWriteArrayList.java:388)
    at java.util.concurrent.CopyOnWriteArrayList.get(CopyOnWriteArrayList.java:397)
    at GFG.main(GFG.java:24)

参考资料: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CopyOnWriteArrayList.html#get-int-