如何使用扫描仪 class 在 Java 中迭代多个字符串输入

Question

我需要从 Java 中的用户获取多行输入。目前我正在使用 Scanner class 来获取输入，但是我正在使用的循环检查每一行没有中断。

当前代码

package getxml;

import java.util.Scanner;


public class Test{

    public static void main(String[] args) {
          
    System.out.println("Enter the Codes: ");   
    Scanner in = new Scanner(System.in);
    
    while(in.hasNextLine()) {
        String nextLine = in.nextLine();
        System.out.println("nextLine:" + nextLine);
    }   
    in.close();
    System.out.println("Scanner closed");
    }
}

预期输入

预期输出

nextLine:10229892
nextLine:10120470
nextLine:10295277
nextLine:10229618
nextLine:10229643
nextLine:10229699
Scanner closed

实际输出

nextLine:10229892
nextLine:10120470
nextLine:10295277
nextLine:10229618
nextLine:10229643
nextLine:10229699

我试过改变

hasNextLine()

到

hasNext()

并添加一个 If 条件以使用以下逻辑跳出循环：

if (nextLine.equals("")) {
    in.close();
    System.out.println("bye");
    break;
}

我需要将in.nextLine()固定到一个变量，否则它会在一个循环中迭代2行。

Answer 1

问题是您的代码不知道用户是否已停止输入代码。

你可以这样做：

public static void main(String[] args) {

    System.out.println("Enter the Codes: ");

    Scanner in = new Scanner(System.in);
    String nextLine = "";
    do{
        nextLine = in.nextLine();
        System.out.println("nextLine:" + nextLine);
    } while(!nextLine.equals("exit"));

    in.close();


    System.out.println("Scanner closed");
}

您的控制台将如下所示：

Answer 2

首先，您必须决定要考虑什么用户输入结束，然后根据该特定条件采取行动。在下面的小例子中，如果用户输入 nothing 那么这将被视为 用户输入结束.

用户输入的所有代码都存储在列表界面对象中。还应用了规则，其中提供的所有代码编号必须是数字并且 长度为八位数字 。 String#matches() method is used for this along with a small Regular Expression（正则表达式）。此外，不能提供重复的代码编号，每个代码编号必须唯一。

当用户完成输入所需的代码后，这些数字将按升序排序并显示在控制台中 window:

System.out.println("Enter the required code numbers (enter nothing when done): ");   
Scanner in = new Scanner(System.in);

List<String> codes = new ArrayList<>();
// Outer loop to keep asking for Code Numbers
while (true) {
    boolean isValid = false; // Flag to ensure a valid entry
    String codeLine = "";
    // inner loop to back up valitity before storing supplied code Number.
    while (!isValid) {    
        System.out.print("Code Line: --> ");
        codeLine = in.nextLine().trim();
        // Break out of this inner loop if nothing is supplied
        if (codeLine.isEmpty()) { break; } 
        // Is the supplied number all digits and are there 8 of them? 
        if (!codeLine.matches("^\d{8}$")) {
            // No...
            System.err.println("Invalid Code Number! Try Again...");
        }
        // Has the supplied number already been previously stored?
        // In other words, is it unique?
        else if (codes.contains(codeLine)) {
            // Already got it! Not Unique!
            System.err.println("Code Number: " + codeLine + " has already been supplied!");
        }
        // Passed validity! Set isValid to true so to exit this inner loop.
        else { isValid = true; }
    }
    // Break out of the outer loop is nothing was supplied.
    if (codeLine.isEmpty()) { break; }
        
    // Validity has been met so Store the the supplied code number.
    codes.add(codeLine);
}
in.close(); // Close the input Stream
System.out.println("Scanner closed");
    
// Sort the Stored Code Numbers in ascending order.
Collections.sort(codes);
    
// Display the Stored Code Numbers...
System.out.println("Code Numbers Entered:");
System.out.println(codes);

Answer 3

“Enter”是输入结束。您正在尝试做的是 simulate 或解决该问题。如果您的 objective 是 只是模拟 多行输入，则以下应该有效：

    public static void main(String[] args) {

        System.out.println("Enter the Codes: ");   
        Scanner in = new Scanner(System.in);
        
        String allLines = "";
        while(in.hasNextLine()) {
            String nextLine = in.nextLine().trim();
            if (nextLine.isEmpty() || nextLine.equals("\r") || nextLine.equals("\r\n") || nextLine.equals("\n")) {
                break;
            }
            allLines += "\r\n" + nextLine;
            //System.out.println("nextLine:" + nextLine);
        }
        System.out.println("all lines:" + allLines);
        in.close();
        
        System.out.println("Scanner closed");
}

如何使用扫描仪 class 在 Java 中迭代多个字符串输入

How to iterate multiple String input in Java using the Scanner class

java

java.util.scanner