MorseCode.java

package Challenge_177_Intermediate;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.util.HashMap;
import java.util.Scanner;

import javax.sound.sampled.AudioFileFormat;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.SourceDataLine;

public final class MorseCode{

	public static final int SAMPLE_RATE = 44100;

	private static final int BITS_PER_SAMPLE = 16;
	private static final int BYTES_PER_SAMPLE = BITS_PER_SAMPLE / 8;
	private static final double MAX_16_BIT = 32767;
	private static final int SAMPLE_BUFFER_SIZE = 4096;

	private static SourceDataLine line;
	private static byte[] buffer;
	private static int bufferSize = 0;

	private static double freq = 440.0;
	private static double[] fullDot;
	private static double[] fullDash;
	private static double[] pause = note(freq, 0.13, 0);

	private static HashMap<Character, String> alphabet = new HashMap<Character, String>();

	static{
		init();
	}

	private static void init(){
		try{
			AudioFormat format = new AudioFormat((float) SAMPLE_RATE, BITS_PER_SAMPLE, 1, true, false);
			DataLine.Info info = new DataLine.Info(SourceDataLine.class, format);

			line = (SourceDataLine) AudioSystem.getLine(info);
			line.open(format, SAMPLE_BUFFER_SIZE * BYTES_PER_SAMPLE);

			buffer = new byte[SAMPLE_BUFFER_SIZE * BYTES_PER_SAMPLE / 3];

			initSounds();
			initHashMap();
		}catch(Exception e){
			e.printStackTrace();
			System.exit(1);
		}
		line.start();
	}

	private static void initSounds(){
		double[] dot = note(freq, 0.125, 1.0);
		double[] dash = note(freq, 0.3, 1.0);
		double[] shortPause = note(freq, 0.05, 0);

		fullDot = new double[dot.length + shortPause.length];
		System.arraycopy(dot, 0, fullDot, 0, dot.length);
		System.arraycopy(shortPause, 0, fullDot, dot.length, shortPause.length);

		fullDash = new double[dash.length + shortPause.length];
		System.arraycopy(dash, 0, fullDash, 0, dash.length);
		System.arraycopy(shortPause, 0, fullDash, dash.length, shortPause.length);
	}

	private static void initHashMap(){
		alphabet.put('A', ".-");
		alphabet.put('B', "-...");
		alphabet.put('C', "-.-.");
		alphabet.put('D', "-..");
		alphabet.put('E', ".");
		alphabet.put('F', "..-.");
		alphabet.put('G', "--.");
		alphabet.put('H', "....");
		alphabet.put('I', "..");
		alphabet.put('J', ".---");
		alphabet.put('K', "-.-");
		alphabet.put('L', ".-..");
		alphabet.put('M', "--");
		alphabet.put('N', "-.");
		alphabet.put('O', "---");
		alphabet.put('P', ".--.");
		alphabet.put('Q', "--.-");
		alphabet.put('R', ".-.");
		alphabet.put('S', "...");
		alphabet.put('T', "-");
		alphabet.put('U', "..-");
		alphabet.put('V', "...-");
		alphabet.put('W', ".--");
		alphabet.put('X', "-..-");
		alphabet.put('Y', "-.--");
		alphabet.put('Z', "--..");
		alphabet.put(' ', "/");
	}

	public static void close(){
		line.drain();
		line.stop();
	}

	public static void play(double in){
		if(in < -1.0) in = -1.0;
		if(in > +1.0) in = +1.0;

		short s = (short) (MAX_16_BIT * in);
		buffer[bufferSize++] = (byte) s;
		buffer[bufferSize++] = (byte) (s >> 8);

		if(bufferSize >= buffer.length){
			line.write(buffer, 0, buffer.length);
			bufferSize = 0;
		}
	}

	public static void play(double[] input){
		for(int i = 0; i < input.length; i++){
			play(input[i]);
		}
	}

	public static void save(String filename, double[] input){
		AudioFormat format = new AudioFormat(SAMPLE_RATE, 16, 1, true, false);
		byte[] data = new byte[2 * input.length];
		for(int i = 0; i < input.length; i++){
			int temp = (short) (input[i] * MAX_16_BIT);
			data[2 * i + 0] = (byte) temp;
			data[2 * i + 1] = (byte) (temp >> 8);
		}

		try{
			ByteArrayInputStream bais = new ByteArrayInputStream(data);
			AudioInputStream ais = new AudioInputStream(bais, format, input.length);
			if(filename.endsWith(".wav")){
				AudioSystem.write(ais, AudioFileFormat.Type.WAVE, new File(filename));
			}else{
				throw new Exception("File format not supported: " + filename + ". Try *.wav");
			}
		}catch(Exception e){
			e.printStackTrace();
			System.exit(1);
		}
	}

	private static double[] note(double hz, double duration, double amplitude){
		int N = (int) (MorseCode.SAMPLE_RATE * duration);
		double[] a = new double[N + 1];
		for(int i = 0; i <= N; i++)
			a[i] = amplitude * Math.sin(2 * Math.PI * i * hz / MorseCode.SAMPLE_RATE);
		return a;
	}

	private static String generateMorseCode(String text){
		String result = "";

		for(int i = 0; i < text.length(); i++){
			result += alphabet.get(text.charAt(i));
			result += " ";
		}

		return result;
	}

	private static double[] generateSound(String morseCode){
		int dot = 0;
		int dash = 0;
		int pause = 0;

		for(int i = 0; i < morseCode.length(); i++){
			switch(morseCode.charAt(i)){
				case '.':
					dot++;
					break;
				case '-':
					dash++;
					break;
				case '/':
					pause++;
					break;
				case ' ':
					pause++;
					break;
			}
		}

		double[] result = new double[dot * MorseCode.fullDot.length + dash * MorseCode.fullDash.length + pause * MorseCode.pause.length];

		int index = 0;
		for(int i = 0; i < morseCode.length(); i++){
			switch(morseCode.charAt(i)){
				case '.':
					for(int j = 0; j < MorseCode.fullDot.length; j++){
						result[index + j] = MorseCode.fullDot[j];
					}
					index += MorseCode.fullDot.length - 1;
					break;
				case '-':
					for(int j = 0; j < MorseCode.fullDash.length; j++){
						result[index + j] = MorseCode.fullDash[j];
					}
					index += MorseCode.fullDash.length - 1;
					break;
				case '/':
					for(int j = 0; j < MorseCode.pause.length; j++){
						result[index + j] = MorseCode.pause[j];
					}
					index += MorseCode.pause.length - 1;
					break;
				case ' ':
					for(int j = 0; j < MorseCode.pause.length; j++){
						result[index + j] = MorseCode.pause[j];
					}
					index += MorseCode.pause.length - 1;
					break;
			}
		}

		return result;
	}

	public static double[] generate(String text){
		text = text.toUpperCase();
		String morseCode = generateMorseCode(text);
		System.out.println(text + " in morse code: " + morseCode);
		return generateSound(morseCode);
	}

	public static void main(String[] args){
		Scanner s = new Scanner(System.in);
		System.out.println("Enter your message in the console!");
		String message = s.nextLine();
		s.close();
		
		save(System.getProperty("user.home") + "/Desktop/Morse_Code.wav", generate(message));
		System.out.println("Done");
		
		MorseCode.close();
		System.exit(0);
	}
}

Hello!

Thanks for your code, but in map mistake for
alphabet.put('U', "..--");

Must be only one dash
alphabet.put('U', "..-");

Thanks for pointing that mistake out!
It's fun to see someone having a look at some of my code that is already almost a decade old.