如何組合字串并制作它的陣列？

我希望用戶輸入 3 個名稱，程式將對其進行 6 種組合。之后，再次要求用戶通過輸入基于名稱組合的數字來選擇名稱。例如，用戶輸入：name1、name2 和 name3。組合為：name1 name2、name1 name 3、name2 name1、name2 name3、name3 name1、name3 name2。并且用戶將通過輸入與組合關聯的數字來從這些組合中進行選擇。我試過這樣做，但無法真正了解如何進行組合。

import java.util.Scanner;
public class Strings1 {

public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    
    System.out.println("Please enter 3 names: ");
    String name1 = input.nextLine();
    String name2 = input.nextLine();
    String name3 = input.nextLine();
    String names[] = {name1, name2, name3};
    
    
    System.out.println("Possible combinations are: ");
    
    for (int i = 1; i <= 6; i  ) {
        System.out.println(i   " - "   names[0]   " "   names[1]);  
    }
}
}

uj5u.com熱心網友回復：

public static void main(String[] args) {
         Scanner input = new Scanner(System.in);

         System.out.println("Please enter 3 names: ");
         String name1 = input.nextLine();
         String name2 = input.nextLine();
         String name3 = input.nextLine();
         String names[] = {name1, name2, name3};
            
         permutationRecursive(names.length, names, ' ');
        
         System.out.println("Possible combinations are: "   combincations.toString());
    }
    
    private static ArrayList<String> combincations = new ArrayList<>();
    
    public static void permutationRecursive(int n, String[] elements, char delimiter) {
        if (n == 1) {
            String combinationString = printArray(elements, delimiter);
            combincations.add(combinationString);
        } else {
            for (int i = 0; i < n - 1; i  ) {
                permutationRecursive(n - 1, elements, delimiter);
                if (n % 2 == 0) {
                    swap(elements, i, n - 1);
                } else {
                    swap(elements, 0, n - 1);
                }
            }
            permutationRecursive(n - 1, elements, delimiter);
        }
    }

    private static void swap(String[] input, int a, int b) {
        String tmp = input[a];
        input[a] = input[b];
        input[b] = tmp;
    }

    private static String printArray(String [] input, char delimiter) {
        StringBuilder strBuilder = new StringBuilder();
        for (int i = 0; i < input.length; i  ) {
            strBuilder.append(input[i]);
            strBuilder.append(delimiter);
        }
        return strBuilder.toString().substring(0, strBuilder.length()-1);
    }

uj5u.com熱心網友回復：

也許你需要一個嵌套回圈：

        int idx = 1;
        for (int i = 0; i < 3; i  ) {
            for (int j = 0; j < 3; j  ) {
                if (i == j) {
                    continue;
                }
                System.out.println((idx  )   " - "   names[i]   " "   names[j]);
            }
        }

或者，更一般的：

    public static void main(String[] args) {
        String[] names = new String[] {"a", "b", "c"};
        List<String[]> combinations = combinations(names);
        System.out.println("Possible combinations are: ");
        for (int i = 0; i < combinations.size(); i  ) {
            System.out.println((i   1)   "-"   combinations.get(i)[0]   " "   combinations.get(i)[1]);
        }
    }

    public static List<String[]> combinations(String[] names) {
        List<String[]> result = new ArrayList<>();
        for (int i = 0; i < names.length; i  ) {
            for (int j = 0; j < names.length; j  ) {
                if (i == j) {
                    continue;
                }
                result.add(new String[] {names[i], names[j]});
            }
        }
        return result;
    }

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