Java程序通过交替取元素来组合两个列表

列表是存储在一起以形成集合的有序元素序列。列表可以包含重复条目和空条目。列表允许我们执行基于索引的操作，即添加、删除、操作和位置访问。 Java提供了一个内置接口 << Java.util>> 来执行列表以及其他基于类的功能。

案例：根据列表的长度，可能会出现两种不同的情况

1. 如果列表 2 在交替添加元素时耗尽，则列表 1 的剩余元素是第二个列表，即列表 1 的剩余元素以相同的出现顺序添加。
2. 如果列表 1 耗尽等等，如上述案例中所述，反之亦然

So, the Aim is to completely remove the elements from second one and add to first one list and whatever is left will be the second list.

方法：采用以下方法将元素交替存储在合并列表中。

• 使用一组元素声明和初始化两个列表。
• 维护两个计数器 i 和 j 以在列表的长度上迭代。循环一直运行到两个列表的较短长度为止。
• 维护一个空列表以存储两个列表的合并内容，顺序是 list1 后跟 list2。
• 在循环结束时，列表中的一个，即较短的一个被用尽。然后使用循环遍历较长列表的剩余元素并将它们一一存储在末尾。
• 合并列表的数据类型应该类似于单个列表。

实现：下面讨论两个例子，同时考虑整数列表和字符串列表

示例 1：字符串列表

Java

// Java Program to Combine Two List
// by Alternatingly Taking Elements
 
// importing required packages
import java.io.*;
import java.util.*;
import java.util.Iterator;
 
// Class to access alterate elements
class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
 
        // Creating(declaring) list1
        List list1 = new ArrayList();
        // Adding elements to list1
        // Custom inputs
        list1.add("Geeks");
        list1.add("Geeks");
        list1.add("portal");
 
        // Creating(declaring) list2
        List list2 = new ArrayList();
 
        // Adding elements to list2
        // Custom inputs
        list2.add("for");
        list2.add("is CSE");
        list2.add("portal");
 
        // Display message
        System.out.print("List1 contents: ");
 
        // Iterating over List1
        Iterator iterator = list1.iterator();
 
        // Condition check using hasNext() which holds true
        // till there is single element remaining in the
        // List
        while (iterator.hasNext()) {
 
            // Printing elements of List 1
            System.out.print(iterator.next() + " ");
        }
 
        // Next Line
        System.out.println();
 
        // Display message
        System.out.print("List2 contents: ");
 
        // Iterating over List 2
        iterator = list2.iterator();
 
        // Condition check using hasNext() which holds true
        // till there is single element remaining in the
        // List
        while (iterator.hasNext()) {
 
            // Printing elements of List 2
            System.out.print(iterator.next() + " ");
        }
 
        // Declaring counters
        int i = 0;
        int j = 0;
 
        // Creating(declaring) merged List
        List merged_list = new ArrayList();
 
        // Iterating over both the lists until
        // the elements of shorter List are exhausted
        while (i < list1.size() && j < list2.size()) {
 
            // Step 1: Adding List1 element
            merged_list.add(list1.get(i));
 
            // Step 2: Adding List2 element
            merged_list.add(list2.get(j));
 
            // Incrementing counters
            i++;
            j++;
        }
 
        // Iterating over the remaining part of List1
        while (i < list1.size()) {
            merged_list.add(list1.get(i));
 
            // Incrementing List1 counter
            i++;
        }
 
        // Iterating over the remaining part of List2
        while (j < list2.size()) {
            merged_list.add(list2.get(j));
 
            // Incrementing List1 counter
            j++;
        }
 
        // Next line
        System.out.println();
 
        // Display message
        System.out.print("Merged List contents: ");
 
        // Iterators
        iterator = merged_list.iterator();
 
        // Iterating over merged List using hasNext() method
        // which holds true till there is single element
        // remaining
        while (iterator.hasNext()) {
 
            // Printing merged list contents
            System.out.print(iterator.next() + " ");
        }
    }
}

输出

List1 contents: Geeks Geeks portal 
List2 contents: for is CSE portal 
Merged List contents: Geeks for Geeks is CSE portal portal 

示例 2：整数列表

Java

// Java Program to Combine Two List
// by Alternatingly Taking Elements
 
// importing required packages
import java.io.*;
import java.util.*;
import java.util.Iterator;
 
// Class
class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
        // Creating(declaring) List1
        List list1 = new ArrayList();
        // Adding elements to List1
        // Custom inputs
        list1.add(2);
        list1.add(4);
        list1.add(6);
 
        // Creating(declaring) List2
        List list2 = new ArrayList();
 
        // Adding elements to List2
        // Custom inputs
        list2.add(1);
        list2.add(3);
        list2.add(5);
        list2.add(7);
 
        // Display message
        System.out.print("List1 contents: ");
 
        // Iterating over List1
        Iterator iterator = list1.iterator();
 
        // ConditionCheck using hasNext() method which hold
        // true till single element in remaining List
        while (iterator.hasNext()) {
 
            // Printing List1 contents
            System.out.print(iterator.next() + " ");
        }
 
        // New line
        System.out.println();
 
        // Display message
        System.out.print("List2 contents: ");
        iterator = list2.iterator();
 
        // ConditionCheck using hasNext() method which hold
        // true till single element in remaining List
        while (iterator.hasNext()) {
 
            // Printing List2 contents
            System.out.print(iterator.next() + " ");
        }
        // Setting counters to zeros
        int i = 0;
        int j = 0;
 
        // Creating(declaring) merged list
        List merged_list
            = new ArrayList();
 
        // Iterating over both the lists
        // until the shorter list
        while (i < list1.size() && j < list2.size()) {
 
            // Step 1: Adding List2 element
            merged_list.add(list2.get(j));
 
            // Step 2: Adding List1 element
            merged_list.add(list1.get(i));
 
            // Incrementing counters
            i++;
            j++;
        }
 
        // Iterating over the remaining part of List1
 
        // Case 1: Input: ShorterList following BiggerList
        while (i < list1.size()) {
 
            // Merge remaining List to List1, and
            // making List2 final as NULL List
            merged_list.add(list1.get(i));
            i++;
        }
 
        // Case 2: Input: BiggerList following ShorterList
        while (j < list2.size()) {
 
            // Merge remaining List to List1,an d
            // making List2 -> NULL List
            merged_list.add(list2.get(j));
            j++;
        }
 
        // New line
        System.out.println();
 
        // Display message
        System.out.print("Merged List contents: ");
 
        // Iterating over merged list
        iterator = merged_list.iterator();
 
        // Condition check using hasNext() method which
        // holds true till there is single element remaining
        // in the List
        while (iterator.hasNext()) {
 
            // Printing merged List contents i.e
            // FinalList = List1 + List2(Null final List)
            System.out.print(iterator.next() + " ");
        }
    }
}

输出

List1 contents: 2 4 6 
List2 contents: 1 3 5 7 
Merged List contents: 1 2 3 4 5 6 7