Java CopyOnWriteArrayList get()用法及代碼示例

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

用法:

public E get(int index)

參數：該函數接受強製參數索引，該參數指定要返回的元素的索引。

返回值：該函數返回給定索引處的元素。

異常：如果索引超出範圍，該函數將拋出IndexOutOfBoundsException。

以下示例程序旨在說明上述函數：

示例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)); 
    } 
}

輸出：

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

示例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)); 
    } 
}

輸出：

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)

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

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