Java

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• writing a JUnit testcase
• serializing Java objects
• using Java logger
• looking up hostnames by IP in Java
• implementing a Queue in Java
• parsing XML files (DOM)
• reading files in java

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Read file in Java

The following example shows ways how to read the contents of a file in Java. The ReadFileToString class reads the contents of a text file into a String.

public class ReadFileToString {
    public static String fileToString(String fileName) {
        File file = new File(fileName);
        StringBuilder contents = new StringBuilder();
        BufferedReader input = null;
        try {
            input = new BufferedReader(new FileReader(file));
            String line = null;
            while((line = input.readLine()) != null)
                contents.append(line);
            return contents.toString();
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            try {
                if(input != null) input.close();
            } catch(Exception e) {
            }
        }
    }
}

Example use:

public class Test {
    public static void main(String[] args) {
        String content = ReadFileToString.fileToString("C:\\MyTextFile.txt");
        System.out.println(content);
    }
}

Dealing with binary files it's more useful to read the file contents into a byte array:

import java.io.InputStream;
import java.io.FileInputStream;
import java.io.File;

public class ReadFileToByteArray {
    public static byte[] read(String fileName) {
        InputStream is = null;
        try {
            File file = new File(fileName);
            is = new FileInputStream(file);
            long length = file.length();
            byte[] bytes = new byte[(int) length];
            int offset = 0;
            int numRead = 0;
            while (offset < bytes.length
                    && (numRead = is.read(bytes, offset, bytes.length - offset)) >= 0) {
                offset += numRead;
            }
            if (offset < bytes.length) {
                throw new RuntimeException("Could not completely read file " + file.getName());
            }
            return bytes;
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            if(is != null) {
                try {
                    is.close();
                } catch(Exception e) {
                    //     
                }
            }
        }
    }
}

Use example:

public class Test {
    public static void main(String[] args) {
        byte[] content = ReadFileToByteArray.read("C:\\MyBinFile.txt");
    }
}