Replace blocks in files, which are identified by a start and an end token.

ReplaceBlocks.java

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

public class ReplaceBlocks {
	private static final String FIRST_LINE_TO_REPLACE = "<<<";
	private static final String LAST_LINE_TO_REPLACE = ">>>";

	private final List<String> replacement;

	public ReplaceBlocks(String pathnameOfReplacement)
			throws FileNotFoundException {
		replacement = readFile(pathnameOfReplacement);
	}

	public void applyTo(String pathname) throws Exception {
		Iterator<String> source = readFile(pathname).iterator();
		FileWriter writer = new FileWriter(pathname);
		copyLinesUntilFirstLineToReplace(source, writer);
		writeReplacementToWriter(writer);
		skipLinesToReplace(source);
		copyUntilEnd(source, writer);
		writer.close();
	}

	private List<String> readFile(String pathname) throws FileNotFoundException {
		File file = new File(pathname);
		Scanner scanner = new Scanner(file);
		List<String> lines = new ArrayList<String>();
		while (scanner.hasNextLine()) {
			lines.add(scanner.nextLine());
		}
		scanner.close();
		return lines;
	}

	private void copyLinesUntilFirstLineToReplace(Iterator<String> source,
			FileWriter writer) throws IOException {
		while (source.hasNext()) {
			String line = source.next();
			if (FIRST_LINE_TO_REPLACE.equals(line)) {
				break;
			} else {
				writeLine(writer, line);
			}
		}
	}

	private void writeReplacementToWriter(FileWriter writer) throws IOException {
		for (String line : replacement) {
			writeLine(writer, line);
		}
	}

	private void skipLinesToReplace(Iterator<String> source) {
		while (source.hasNext()) {
			String line = source.next();
			if (LAST_LINE_TO_REPLACE.equals(line)) {
				break;
			}
		}
	}

	private void copyUntilEnd(Iterator<String> source, FileWriter writer)
			throws IOException {
		while (source.hasNext()) {
			String line = source.next();
			writeLine(writer, line);
		}
	}

	private void writeLine(FileWriter writer, String line) throws IOException {
		writer.write(line);
		writer.write("\n");
	}

	public static void main(String[] args) throws Exception {
		ReplaceBlocks replacer = new ReplaceBlocks(args[0]);
		for (int i = 1; i < args.length; ++i) {
			replacer.applyTo(args[i]);
		}
	}
}