如何使用Java语言以相反的顺序输出？

Question

我面临一个问题，从标准输入中取出所有行并将它们以相反的顺序写入标准输出。 即以输入的相反顺序输出每一行。

下面是我的代码：

  import java.util.Scanner;

  public class ReverseOrderProgram {
   public static void main(String args[]) {
    //get input
    Scanner sc = new Scanner(System.in);
    System.out.println("Type some text with line breaks, end by 
    \"-1\":");
    String append = "";
    while (sc.hasNextLine()) {
        String input = sc.nextLine();
        if ("-1".equals(input)) {
            break;
        }
        append += input + " ";
    }
    sc.close();
    System.out.println("The current append: " + append);
    String stringArray[] = append.split(" strings" + "");



    System.out.println("\n\nThe reverse order is:\n");

    for (int i = 0; i < stringArray.length; i++) {

        System.out.println(stringArray[i]);
    }
   }
  }

当我使用如下示例输入运行代码时：

  Type some text with line breaks, end by "-1":
  My name is John.
  David is my best friend.
  James also is my best friend.
  -1

我得到以下输出：

  The current append: My name is John. David is my best friend. James also is my best friend.


  The reverse order is:

  My name is John. David is my best friend. James also is my best friend.

然而，所需的输出如下所示：

  The current append: My name is John. David is my best friend. James also is my best friend.


  The reverse order is:

  James also is my best friend.
  David is my best friend. 
  My name is John.

谁能帮我检查一下我的代码有什么问题并修复它？

Answer 1

试试下面的代码。

import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;

public class ReverseOrderProgram {
public static void main(String args[]) {

    Scanner sc = new Scanner(System.in);
    System.out.println("Type some text with line breaks, end by\"-1\":");
    List<String> list= new LinkedList<String>();
    String append = "";
    while (sc.hasNextLine()) {
        String input = sc.nextLine();
        if ("-1".equals(input)) {
            break;
        }
        list.add(input);
    }
    sc.close();
    System.out.println("The current append: " + append);

    Collections.reverse(list);
    for (String string : list) {
        System.out.println(string);
    }
  }
}

希望对你有帮助

Answer 2

而不是将 input 附加到 append 字符串，您应该将输入字符串添加到 List，然后从底部或使用 Collections.reverse() 方法，然后直接打印出来

Answer 3

编辑 - 与之前的答案基本相同，但使用 for 循环：

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

public class ReverseOrderProgram {
    public static void main(String args[]) {

    //create arraylist for lines
    ArrayList<String> lines = new ArrayList<String>();
    //get input

    Scanner sc = new Scanner(System.in);
    System.out.println("Type some text with line breaks, end by \"-1\":");
    String append = "";
    while (sc.hasNextLine()) {
        String input = sc.nextLine();
        if ("-1".equals(input)) {
            break;
        }
        lines.add(input);
    }

    sc.close();
    System.out.println("The current append: ");
    for(String line : lines){
        System.out.print(line + ". ");
    }

    System.out.println("\n\nThe reverse order is:\n");

    for (int i = lines.size()-1; i >=0 ; i--) {
        System.out.println(lines.get(i));
    }
}
}

Answer 4

1 - 1 种方法是从 backword 运行循环。

for (int i = stringArray.length; i >=0 ; i++) {

    System.out.println(stringArray[i]);
}

2 - 在列表中使用 Collections.reverse() 方法并打印它。喜欢

    List<String> list = Arrays.asList(stringArray); 

    Collections.reverse(list ); 

    System.out.println("Modified List: " + list ); 

Answer 5

您可以使用具有 LIFO 行为的 Stack 数据结构来插入和读取元素。更完整的 Java Stack 实现是 Deque，它具有“descendingOrder”方法，该方法以相反的顺序返回元素的迭代器。

        Deque deque = new LinkedList();

        // We can add elements to the queue in various ways
        deque.add("Element 1 (Tail)"); // add to tail
        deque.addFirst("Element 2 (Head)");
        deque.addLast("Element 3 (Tail)");
        deque.push("Element 4 (Head)"); //add to head
        deque.offer("Element 5 (Tail)");
        deque.offerFirst("Element 6 (Head)");
        deque.offerLast("Element 7 (Tail)");

        Iterator reverse = deque.descendingIterator();
        System.out.println("Iterating over Deque with Reverse Iterator");
        while (reverse.hasNext()) {
            System.out.println("\t" + reverse.next());
        }

Answer 6

您可以按照其他答案的建议使用Collections.reverse()。但是标准的反转方式是使用Stack 完成的。 Stack 是一个 LIFO 数据结构，它准确地展示了您所需的行为。您需要将所有结果推送到Stack 和pop，直到Stack 变为empty。像下面 sn-p 这样的东西会给你一个大纲。

String input = " Hello \n World \n Here you go";
List<String> inputList = Arrays.asList(input.split("\n"));
        Stack<String> myStringStack = new Stack<>();
        myStringStack.addAll(inputList); // This is to exhibit your input scenario from user.
        while (!myStringStack.isEmpty()) { // While your stack is not empty, keep popping!
            System.out.println(myStringStack.pop());
         }