需要弄清楚如何替换 space 的数组列表中的逗号

Question

我已经尝试使用 replaceAll 和 removeAll 但仍然无法更改没有逗号的列表。我试着在 list + "") 之后添加；但没有任何改变。仍然得到带逗号的输出。我需要删除输出中的逗号。数字之间只需要一个白色 space。（见最后的输出）

(Remove duplicates) Write a method that removes the duplicate elements from an array list of integers using the following header:
public static void removeDuplicate(ArrayList<Integer> list)
Write a test program that prompts the user to enter 10 integers to a list and displays the distinct integers separated by exactly one space.

package exercise11_13;

import java.util.ArrayList;
import java.util.Scanner;

public class Exercise11_13 {

    /**
     * @param args the command line arguments
     */
    // Main method
    public static void main(String[] args) {
        // Create de Scanner object.
        Scanner input = new Scanner(System.in);
        
        // Prompt the user to enter ten integer numbers. 
        System.out.print("Please, enter ten (10) integers numbers: ");
        
        // Create the ListArray (List object).
        ArrayList<Integer> list = new ArrayList<>();
        for (int i = 0; i < 10; i++) list.add(input.nextInt());

        removeDuplicate(list);
        
        System.out.println("Display the distinct integers in their input order "
                + "and seperated by exactly one space: " + "\n" + list );
    }

    public static void removeDuplicate(ArrayList<Integer> list) {

        ArrayList<Integer> temp = new ArrayList<>();
        for (int i = 0; i < list.size(); i++) {

            if (!temp.contains(list.get(i))) {
                temp.add(list.get(i));
            }
        }
        list.clear();
        list.addAll(temp);
        
    }
}

输出：我需要删除输出中的逗号。数字之间只需要一个白色 space。运行:

Please, enter ten (10) integers numbers: 78
99
54
63
56
78
63
14
67
99
Display the distinct integers in their input order and seperated by exactly one space: 
[78, 99, 54, 63, 56, 14, 67]
BUILD SUCCESSFUL (total time: 27 seconds)

Answer 1

当您使用这样的对象时，它会通过其 toString 方法隐式转换为字符串。您不应该依赖列表的 toString 实现，而是将其转换为您自己需要的字符串。在这里，您可以流式传输列表并使用 space:

加入它

System.out.println(
   "Display the distinct integers in their input order and separated by exactly one space: \n" + 
   list.stream().map(Object::toString).collect(Collectors.joining(" "))
);

Answer 2

由于问题是用 replaceAll 标记的，因此确实可以使用正则表达式 [,\[\]] 删除 List::toString 方法（方括号和逗号）提供的所有“冗余”字符（括号应该用 \ 转义）：

List<Integer> list = Arrays.asList(1, 2, 3, 4, 5);
System.out.println(list.toString().replaceAll("[,\[\]]", "")); // 1 2 3 4 5

或者，知道括号是第一个和最后一个字符，可以在 substring 的帮助下将它们删除，然后应用 String::replace:

String str = list.toString();
    
System.out.println(str.substring(1, str.length() - 1).replace(",", "")); // 1 2 3 4 5

Answer 3

在这个程序中有两种方法可以替换白色space的逗号。

长篇：需要添加：导入 java.util.stream.Collectors;

System.out.println("Display the distinct integers in their input "
                + "order and separated by exactly one space: "
                + "\n" 
                + 
                list.stream().map(Object::toString).collect(Collectors.joining("")));

短的：

System.out.println("\nDisplay the distinct integers in their input "
                + "order and separated by exactly one space: "
                + "\n" + list.toString().replaceAll("[,\[\]]", ""));

下面是整个程序。

package exercise11_13;

import java.util.ArrayList;
import java.util.Scanner;
import java.util.stream.Collectors;

    public class Exercise11_13 {
    
        /**
         * @param args the command line arguments
         */
        // Main method
        public static void main(String[] args) {
            // Create de Scanner object.
            Scanner input = new Scanner(System.in);
            
            // Prompt the user to enter ten integer numbers. 
            System.out.print("Please, enter ten (10) integers numbers: ");
            
            // Create the ListArray (List object).
            ArrayList<Integer> list = new ArrayList<>();
            for (int i = 0; i < 10; i++) list.add(input.nextInt());
    
            removeDuplicate(list);
            /**
            System.out.println("Display the distinct integers in their input "
                    + "order and separated by exactly one space: "
                    + "\n" + 
            list.stream().map(Object::toString).collect(Collectors.joining(" ")));
            */
            System.out.println("\nDisplay the distinct integers in their input "
                    + "order and separated by exactly one space: "
                    + "\n" + list.toString().replaceAll("[,\[\]]", ""));         
        }
    
        public static void removeDuplicate(ArrayList<Integer> list) {
    
            ArrayList<Integer> temp = new ArrayList<>();
            for (int i = 0; i < list.size(); i++) {
    
                if (!temp.contains(list.get(i))) {
                    temp.add(list.get(i));
                }
            }
            list.clear();
            list.addAll(temp);
            
        }
    }

需要弄清楚如何替换 space 的数组列表中的逗号

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