Mindmelt.java

import java.util.Scanner;
import java.util.Stack;

public class Mindmelt {

	public static void main(String[] args) {
		try (Scanner scanner = new Scanner(System.in)) {
			Interpreter interpreter = new Interpreter(scanner.nextLine().toCharArray());

			String command;

			while (scanner.hasNextLine() && (command = scanner.nextLine()) != null) {
				if (command.trim().isEmpty())
					break;
				interpreter.interpret(command.toCharArray());
			}
		}
	}

	static class Interpreter {

		Interpreter(char[] i) {
			this.inputBuffer = i;
		}

		char[] inputBuffer;
		byte[] memory = new byte[30_000];
		int pointer, read;
		Stack<Integer> jumps = new Stack<>();

		void interpret(char[] commands) {
			for (int index = 0; index < commands.length; index++) {
				char command = commands[index];
				switch (command) {
					case '+':
						memory[pointer]++;
						break;
					case '-':
						memory[pointer]--;
						break;
					case '>':
						pointer++;
						break;
					case '<':
						pointer--;
						break;
					case '[':
						if (memory[pointer] != 0)
							jumps.push(index);
						break;
					case ']':
						int jmp = jumps.pop();
						if (memory[pointer] != 0)
							index = jmp - 1;
						break;
					case '.':
						System.out.print(Character.toChars(memory[pointer]));
						break;
					case ',':
						memory[pointer] = (byte) ((char) inputBuffer[read++]);
						break;
					default:
						break;
				}
			}
		}

	}

}