How can I get a line from a file based on a condtion in java

Question

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Hi , I have a file which i am reading line by line.for e.g

Java

package com.java2novice.files;
 
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
 
public class ReadLinesFromFile {
 
    public static void main(String a[]){
        BufferedReader br = null;
        String strLine = "";
        try {
            br = new BufferedReader( new FileReader("fileName"));
            while( (strLine = br.readLine()) != null){
                System.out.println(strLine);
            }
        } catch (FileNotFoundException e) {
            System.err.println("Unable to find the file: fileName");
        } catch (IOException e) {
            System.err.println("Unable to read the file: fileName");
        }
    }
}

I want to extract a single line from the file , if the line contains "Lets C++".
i.e if a line contains "Lets C++", store the entire line in a string.
Can anyone help me in getting this.

Thanks in advance

Posted 21-Jan-16 2:49am

Member 12018498

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Comments

Sergey Alexandrovich Kryukov 21-Jan-16 11:06am

How about reading all the file into the array of lines or digest it all in some highly usable data structure? Is the file too big for that?

One little problem is: the lines have different lengths, so you don't know the location of each line in advance, before you read the whole file. So, another solution would be reading the whole file preliminarily, to digest it into the information on how to locate each line. This data structure could be further used to read any of those lines on demand.

—SA

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Richard MacCutchan · Accepted Answer · 2016-01-21T05:21:00

Solution 1

See String.contains (Java Platform SE 7 )[^].

Posted 21-Jan-16 5:21am

Richard MacCutchan

Sri Nivas (Vasu) · Accepted Answer · 2016-01-21T05:24:00

What you need is change below

C#

while( (strLine = br.readLine()) != null){
               System.out.println(strLine);
           }

TO

C#

while( (strLine = br.readLine()) != null){
              if( strLine.toLowerCase().contains("Lets C++".toLowerCase())
             {
                  System.out.println(strLine);
             }
          }