如何在Java中交换 ArrayList 中的两个元素？

我们可以使用 Collections.swap() 方法交换 Array List 的两个元素。此方法接受三个参数。第一个参数是 ArrayList，另外两个参数是元素的索引。此方法不返回任何内容。

句法：

public static void swap(List list, int a, int b);

编程需要懂一点英语

参数

list : 一个ArrayList或任何 List 实现类，在其中交换元素
a：第一个元素的索引
b : 第二个元素的索引

例外：如果 Array List 的索引小于 0 或大于 ArrayList 的大小，则抛出IndexOutOfBoundsException 。

示例 1

Java

// Java program to swap two elements in an ArrayList
 
import java.util.ArrayList;
import java.util.Collections;
 
public class GFG {
 
    public static void main(String a[])
    {
 
        // Create the Array List
        ArrayList ArrList = new ArrayList();
 
        // add the values in Array List
        ArrList.add("Item 1");
        ArrList.add("Item 2");
        ArrList.add("Item 3");
        ArrList.add("Item 4");
        ArrList.add("Item 5");
 
        // display Array List before swap
        System.out.println("Before Swap the ArrayList ");
        System.out.println(ArrList);
 
        // Swapping the elements at 1 and 2 indices
        Collections.swap(ArrList, 1, 2);
 
        // display Array List after swap
        System.out.println("After Swap the ArrayList");
        System.out.println(ArrList);
    }
}

Java

// Java program to swap two elements in an ArrayList
 
import java.util.ArrayList;
import java.util.Collections;
 
public class GFG {
 
    public static void main(String a[]) throws Exception
    {
 
        // Create the Array List
        ArrayList ArrList = new ArrayList();
 
        // add the values in Array List
        ArrList.add("Item 1");
        ArrList.add("Item 2");
        ArrList.add("Item 3");
        ArrList.add("Item 4");
        ArrList.add("Item 5");
 
        // display Array List before swap
        System.out.println("Before Swap the ArrayList ");
        System.out.println(ArrList);
 
        // Swapping the elements at -1 and 2 indices
        // Throws IndexOutOfBounds Exception
        Collections.swap(ArrList, -1, 2);
    }
}

输出

Before Swap the ArrayList 
[Item 1, Item 2, Item 3, Item 4, Item 5]
After Swap the ArrayList
[Item 1, Item 3, Item 2, Item 4, Item 5]

示例 2

Java

// Java program to swap two elements in an ArrayList
 
import java.util.ArrayList;
import java.util.Collections;
 
public class GFG {
 
    public static void main(String a[]) throws Exception
    {
 
        // Create the Array List
        ArrayList ArrList = new ArrayList();
 
        // add the values in Array List
        ArrList.add("Item 1");
        ArrList.add("Item 2");
        ArrList.add("Item 3");
        ArrList.add("Item 4");
        ArrList.add("Item 5");
 
        // display Array List before swap
        System.out.println("Before Swap the ArrayList ");
        System.out.println(ArrList);
 
        // Swapping the elements at -1 and 2 indices
        // Throws IndexOutOfBounds Exception
        Collections.swap(ArrList, -1, 2);
    }
}

输出

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index -1 out of bounds for length 5
    at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
    at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
    at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248)
    at java.base/java.util.Objects.checkIndex(Objects.java:372)
    at java.base/java.util.ArrayList.get(ArrayList.java:458)
    at java.base/java.util.Collections.swap(Collections.java:501)
    at GFG.main(GFG.java:27)