Evaluation of Postfix Expression.java

import java.util.Stack;
public class Test {
	static int evaluatePostfix(String exp)
	{
		Stack<Integer> stack = new Stack<>();
		for (int i = 0; i < exp.length(); i++) {
			char c = exp.charAt(i);
			if (Character.isDigit(c))
				stack.push(c - '0');
			else {
				int val1 = stack.pop();
				int val2 = stack.pop();

				switch (c) {
				case '+':
					stack.push(val2 + val1);
					break;
				case '-':
					stack.push(val2 - val1);
					break;
				case '/':
					stack.push(val2 / val1);
					break;
				case '*':
					stack.push(val2 * val1);
					break;
				}
			}
		}
		return stack.pop();
	}
	public static void main(String[] args)
	{
		String exp = "231*+9-";
		System.out.println("postfix evaluation: "
						+ evaluatePostfix(exp));
	}
}