从 java 中的文本文件打印包含特定模式的行

Question

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

// The name of the file to open.
 System.out.print("\nPlease enter TextfileName.txt : ");
Scanner keyboard = new Scanner(System.in); 
String fileName = keyboard.next();
int counter = 0;

  //Reading filename.text from code
  System.out.println("\nReading '"+fileName+"' from Java Code.\n");

 //Date and time stamp for the program. 
  DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
  Date date = new Date();

  System.out.print("Todays date: "+dateFormat.format(date)+"\n\n\n");

// This will reference one line at a time
String line = null;
FileReader fileReader = null;

//-------------------------------------------------------TAB_1----------------------------------------------//
        System.out.println("\t\t\t\t TAB_1[Date on]\n");
try {
    // FileReader reads text files in the default encoding.
    fileReader = new FileReader(fileName);

    // Always wrap FileReader in BufferedReader.
    BufferedReader bufferedReader = new BufferedReader(fileReader);


    while((line = bufferedReader.readLine()) != null) {
        counter++;
        if(counter == 1 || counter == 3 || counter == 9)
        {
           // print out the lines above that are found in the text
           System.out.println(line);
           System.out.println("----------");
        }
    }   
  }    

      catch(FileNotFoundException ex) {
            System.out.println("Unable to open file '" + fileName + "'");                
           }
               catch(IOException ex) {
           System.out.println("Error reading file '" + fileName + "'");                  
    // Or we could just do this: 
    // ex.printStackTrace();
}
finally
{
    if(fileReader != null){
       // Always close files.
      // BufferedReader.close();            
    }
}

some matcher would help, but i`m not sure how it works

}}

The one i have above is working but i want to also find a specific string anywhere in the text-file and print that line

Answer 1

Just use the contains method of the String class to check for occurances of a substring inside a string.

while((line = bufferedReader.readLine()) != null) {
        if (line.contains("some string") {
           System.out.println(line);
           System.out.println("----------");
        }
    }   

If you wish to check multiple substrings and not just one then you should create a String array of all the substrings you want to look for and loop through them.

First add the following line at the beggining of the class :

public static final String[] listOfStrings = new String[] { "substring 0", "sub string 1" , "substring 2" }; 

Replace the substrings with your own values.

Then, loop through them to find matches:

   while((line = bufferedReader.readLine()) != null) {
       for (String match : listOfStrings) {        
            if (line.contains(match)) {
                System.out.println(line);
                System.out.println("----------");
                break; // No need to continue after the first match
            }
        } 
    }