How do I generate random string?

package org.kodejava.example.security;

import java.security.SecureRandom;
import java.util.Random;

public class RandomString {
    public static final String SOURCES =
            "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";

    public static void main(String[] args) {
        RandomString rs = new RandomString();
        System.out.println(rs.generateString(new Random(), SOURCES, 10));
        System.out.println(rs.generateString(new Random(), SOURCES, 10));
        System.out.println(rs.generateString(new SecureRandom(), SOURCES, 15));
        System.out.println(rs.generateString(new SecureRandom(), SOURCES, 15));
    }

    /**
     * Generate a random string.
     *
     * @param random the random number generator.
     * @param characters the characters for generating string.
     * @param length the length of the generated string.
     * @return
     */
    public String generateString(Random random, String characters, int length) {
        char[] text = new char[length];
        for (int i = 0; i < length; i++) {
            text[i] = characters.charAt(random.nextInt(characters.length()));
        }
        return new String(text);
    }
}

Example string produced by the code snippets are:

uxEUFqTqS0
vr89vdF4gh
ysYF9XEHhO5FtDf
aBANhrLObZ1XLJi

How do I convert InputStream to String?

This example will show you how to convert an InputStream into String. In the code snippet below we read a data.txt file, could be from common folder or from inside a jar file.

package org.kodejava.example.io;

import java.io.*;

public class StreamToString {

    public static void main(String[] args) throws Exception {
        StreamToString sts = new StreamToString();

        // Get input stream of our data file. This file can be in
        // the root of you application folder or inside a jar file
        // if the program is packed as a jar.
        InputStream is = sts.getClass().getResourceAsStream("/data.txt");

        // Call the method to convert the stream to string
        System.out.println(sts.convertStreamToString(is));
    }

    public String convertStreamToString(InputStream is) throws IOException {
        // To convert the InputStream to String we use the
        // Reader.read(char[] buffer) method. We iterate until the
        // Reader return -1 which means there's no more data to
        // read. We use the StringWriter class to produce the string.
        if (is != null) {
            Writer writer = new StringWriter();

            char[] buffer = new char[1024];
            try {
                Reader reader = new BufferedReader(
                        new InputStreamReader(is, "UTF-8"));
                int n;
                while ((n = reader.read(buffer)) != -1) {
                    writer.write(buffer, 0, n);
                }
            } finally {
                is.close();
            }
            return writer.toString();
        }
        return "";
    }
}