TextFile.java

package com.brianway.learning.java.io;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.TreeSet;

/**
 * Static functions for reading and writing text files as
 * a single string, and treating a file as an ArrayList.
 */
public class TextFile extends ArrayList<String> {
    // Read a file as a single string:
    public static String read(String fileName) {
        StringBuilder sb = new StringBuilder();
        try {
            BufferedReader in = new BufferedReader(
                    new FileReader(
                            new File(fileName).getAbsoluteFile()));
            try {
                String s;
                while ((s = in.readLine()) != null) {
                    sb.append(s);
                    sb.append("\n");
                }
            } finally {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        return sb.toString();
    }

    // Write a single file in one method call:
    public static void write(String fileName, String text) {
        try {
            PrintWriter out = new PrintWriter(
                    new File(fileName).getAbsoluteFile());
            try {
                out.print(text);
            } finally {
                out.close();
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    // Read a file, split by any regular expression:
    public TextFile(String fileName, String splitter) {
        super(Arrays.asList(read(fileName).split(splitter)));
        // Regular expression split() often leaves an empty
        // String at the first position:
        if (get(0).equals("")) remove(0);
    }

    // Normally read by lines:
    public TextFile(String fileName) {
        this(fileName, "\n");
    }

    public void write(String fileName) {
        try {
            PrintWriter out = new PrintWriter(
                    new File(fileName).getAbsoluteFile());
            try {
                for (String item : this)
                    out.println(item);
            } finally {
                out.close();
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    // Simple test:
    public static void main(String[] args) {
        String parent = TextFile.class.getResource("/").getPath();
        String inFileName = parent + "/infile.txt";

        String file = read(inFileName);
        write(parent + "/text.txt", file);
        TextFile text = new TextFile(parent + "/text.txt");
        text.write(parent + "test2.txt");
        // Break into unique sorted list of words:
        TreeSet<String> words = new TreeSet<String>(
                new TextFile(inFileName, "\\W+"));
        // Display the capitalized words:
        System.out.println(words.headSet("a"));

    }
}