使用扫描仪跳过特定行

Question

I wrote this code to read a text file and I am running into a problem where it skips the 4th line rather than a line that meets the condition.

Here's my code:

    while(fileReader.hasNext()) {
                        String label = fileReader.nextLine();
                        String prompt = fileReader.nextLine();
                        String message = fileReader.nextLine();
                        
                        if(fileReader.nextLine().contains(label)) {
                            fileReader.nextLine();
                        }
                        
                        System.out.println(label);
                        System.out.println(prompt);
                        System.out.println(message);
    }           

The prompt that I am trying to read is this. In this case, I want to skip every line that contains information about the number of children a node has. (Line 4(root 3) and 14(1 3))

root                                       // Will always be "root"
Root Node                                  // Will never be displayed to screen
What Model is the Washing Machine?         // Message
root 3                                     // Number of children for label root: 3
1                                          // First child. Label
WM200                                      // First child. Prompt
What is the problem?                       // First child. Message
2                                          // Second child. Label
WM300                                      // Second child. Prompt
What is the problem?                       // Second child. Message
3                                          // Third child. Label
WM400                                      // Third child. Prompt
What is the problem?                       // Third child. Message
1 3                                        // Number of children for label 1: 3
1-1                                        // Label
No Water.                                  // Prompt
Is the hose attached?                      // Message, etc.

Desired Output:

root                                       // Will always be "root"
Root Node                                  // Will never be displayed to screen
What Model is the Washing Machine?         // Message
1                                          // First child. Label
WM200                                      // First child. Prompt
What is the problem?                       // First child. Message
2                                          // Second child. Label
WM300                                      // Second child. Prompt
What is the problem?                       // Second child. Message
3                                          // Third child. Label
WM400                                      // Third child. Prompt
What is the problem?                       // Third child. Message
1-1                                        // Label
No Water.                                  // Prompt
Is the hose attached?                      // Message, etc.

And I am getting the following output from my code:

root                                     
Root Node                                 
What Model is the Washing Machine?         
1                                           
WM200                                       
What is the problem?                        
WM300                                       
What is the problem?                       
3                                          
What is the problem?                        
1 3                                         
1-1                                         
Is the hose attached?    

So my code ends up skipping every fourth line rather than only those lines that meet the condition.

Answer 1

You read the line in the if condition without storing it you should use:

while (fileReader.hasNext()) {
    String label = fileReader.nextLine();
    String prompt = fileReader.nextLine();
    String message = fileReader.nextLine();

    String line = fileReader.nextLine();
    if (line.contains(label)) {
        line = fileReader.nextLine();
    }

    // continue your logic with the stored line
    System.out.println(label);
    System.out.println(prompt);
    System.out.println(message);
}     

  

Answer 2

So you are trying to rebuild a Tree which has been persisted (breadth-first) into this text. The question you ask is not the correct one as the data is not being read correctly. Looking at the text and your comment...

 1 3                                        // Number of children for label 1: 3

Clearly this is nothing to do with the label of node 3 appearing a few lines before. Your data format is:

• Node uses 3 lines only
• Children block starts with "parent count" followed by count Node s.

Try this:

    Pattern regex = Pattern.compile("^(\\S+) (\\d+)"); // Header is "<parent-label> <count>"
    String parent = null;
    
    while (fileReader.hasNext()) {
      String header = fileReader.nextLine(); // new stanza - could be Node or Children
      Matcher m = regex.matcher(header);
      if (m.find()) {
        // Handle Children
        parent = m.group(1);
      } else {
        // Handle Node
        String label = header;
        String prompt = fileReader.nextLine();
        String message = fileReader.nextLine();

        System.out.println(String.format("%s/%s %s %s", parent, label, prompt, message));
      }
    }