Java String Memory Leak

Question

I am not java expert.

My code is reading a file into a String. This code gets executed every 5 minutes. The size of file varies. Sometimes it is 100 sometimes it is 1000 lines.

I am experience Out Of Memory, after some days.

The question I have is, when my codes goes out of scope of the Reading file function, does Java garbage collect the String?

I am pretty confused by reading on the internet. Some people says it does not get deleted and use StringBuffer.

// Demonstrate FileReader.

import java.io.*;
class FileReaderDemo {
    public static void read(BufferedReader br) throws Exception {
        long length = 0;
        String s;
        while (true) {
            s = br.readLine();
            s += "abcd";
            if (s == null) {
                break;
            }
            length += s.length();
            //System.out.println(s);
        }
        System.out.println("Read: " + (length / 1024 / 1024) + " MB");
    }

    public static void main(String args[]) throws Exception {
        //FileReader fr = new FileReader("FileReaderDemo.java");
        FileReader fr = new FileReader("big_file.txt.1");
        BufferedReader br = new BufferedReader(fr);
        String s;
        read(br);
        fr = new FileReader("big_file.txt.1");
        br = new BufferedReader(fr);
        read(br);
        fr = new FileReader("big_file.txt.1");
        br = new BufferedReader(fr);
        read(br);
        fr = new FileReader("big_file.txt.1");
        br = new BufferedReader(fr);
        read(br);
        BufferedReader in = new BufferedReader(new InputStreamReader(System. in )); in .readLine();
        fr.close();
    }
}

Answer 1

Hello, I am not java expert.

Everyone has something they can learn.

My code is reading a file into a String, This code gets executed every 5 minutes. Now Sometime file size of 100 lines sometimes 1000 lines.

Doesn't sound very large or very often. Shouldn't be a problem.

I am experience Out Of Memory, after some days.

You should be able to get a heap dump and see where you have run out of memory and why.

Question I have is, When my codes goes out of scope of the Reading file Function. Does Java Garbage collect the String .

It can be collected when it is no longer reachable via a Strong reference.

I am pretty confuse by reading on internet some says it does not get deleted and use StringBuffer

Sounds like you came to the right place. I have never heard that one.

Answer 2

Your read method will never terminate. Once you reach the end of the file, you just continue adding the string "nullabcd" to s, forever.

EDIT: forget that, s is re-assigned each time. Still, I can't see how your read method can terminate.