How to read last 5 lines of a .txt file into java

Question

I have a text file that consists of several entries such as:

hello
there
my
name
is
JoeBloggs

How would I read the last five entries in des

Answer 1

First you have to read the file line by line and add each line to a list. Once the file is read completely, you can print each element in the list in reverse order as shown below:

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;


public class FileReader {

    public static List<String> readFile() throws IOException {
        List<String> fileContents = new ArrayList<String>();
        FileInputStream fileInputStream = new FileInputStream("C:/Users/compaq/Desktop/file.txt");
        InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);
        BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
        String strLine = null;
        while((strLine=bufferedReader.readLine())!=null) {
            fileContents.add(strLine);
        }
        fileInputStream.close();
        return fileContents;
    }

    public static void printFileInReverse(List<String> fileContents, int numberOfLines) {
        int counter = 0;
        for(int i=(fileContents.size()-1);i>=0;i--) {
            if(counter==numberOfLines) { break; }
            System.out.println(fileContents.get(i));
            counter++;
        }
    } 

    public static void main(String[] args) throws IOException {
        List<String> fileContents = new ArrayList<String>();
        fileContents = FileReader.readFile();
        int numberOfLines = 5;// Number of lines that you would like to print from the bottom of your text file.
        FileReader.printFileInReverse(fileContents, numberOfLines);
    }

}

Answer 2

Please try this code. It is working fine for me.

public static void main(String[] args)
{
    try
    {
        int numOfLastline = 10;
        BufferedReader reader = new BufferedReader(new FileReader("Text.txt"));
        int lines = 0;
        while (reader.readLine() != null)
            lines++;
        reader.close();

        System.out.println(lines);

        String printedLine = null;
        List<String> listForString = new ArrayList<String>();
        for (int i = lines - 1; i >= (lines - numOfLastline); i--)
        {
            printedLine = (String) FileUtils.readLines(new File("Text.txt"), "ISO-8859-1").get(i);
            System.out.println(printedLine);
            listForString.add(printedLine);
        }

        System.out.println("\n\n============ Printing in Correct order =============\n\n");
        Collections.reverse(listForString);

        for (int k = 0; k < listForString.size() ; k++)
        {
            System.out.println(listForString.get(k));
        }

    }
    catch (Exception e)
    {
        e.printStackTrace();
    }
}

Note : Provide your needed last line numbers at numOfLastline and file [instead of this Text.txt].

Answer 3

Try this code, a list of length 5 is scanned through all the lines, finally the list is reversed. I edited / modified your code, test it to see it's fully working.

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

public class Test
{
    public static void main(String[] args) throws Exception
    {
        ArrayList<String> bandWidth = new ArrayList<String>();
        FileInputStream in = new FileInputStream("file.txt");
        BufferedReader br = new BufferedReader(new InputStreamReader(in));

        String tmp;
        while ((tmp = br.readLine()) != null)
        {
            bandWidth.add(tmp);
            if (bandWidth.size() == 6)
                bandWidth.remove(0);
        }

        ArrayList<String> reversedFive = new ArrayList<String>();
        for (int i = bandWidth.size() - 1; i >= 0; i--)
            reversedFive.add(bandWidth.get(i));
        in.close();
    }
}

Answer 4

If all it really does have to do is print last 5 lines:

        ArrayList<String> lines = new ArrayList<String>();

        String tmp="";
        while ((tmp = br.readLine()) != null) {
            lines.add(tmp);
        }
        for (int i = lines.size()-5; i < lines.size(); i++) {
            System.out.println(lines.get(i-1));
        }

Answer 5

One very easy way would be to use the CircularFifoBuffer class from the Apache Commons Collections library. It's basically a list of a fixed size that discards old elements when it's full and you add new ones. So you'd create a CircularFifoBuffer of size 5, then add all the lines to it. At the end, it'd contain just the last five lines of the file.

Answer 6

Try this. This give for last 5 line.

 public static void main(String[] args) throws IOException {
            List<String > list =new ArrayList<String>();
            FileInputStream in = new FileInputStream("C:/adminconsole.txt");
            BufferedReader br = new BufferedReader(new InputStreamReader(in));

            String strLine ="", tmp;
            while ((tmp = br.readLine()) != null){ 
                //strLine =tmp+"\n"+strLine;
                list.add(tmp);
                }

            if(list.size()>5){
                for (int i=list.size()-1; i>=(list.size()-5); i--) {
                    System.out.println(list.get(i));
                }
            }else{
                for (int i=0; i<5; i++) {
            System.out.println(list.get(i));
        }

            }

        }
    }