øving3

src/main/java/oving3/RPNCalc.java

@@ -0,0 +1,63 @@
+package oving3;
+
+import java.util.Stack;
+
+public class RPNCalc {
+
+	private Stack<Double> stack = new Stack<>();
+
+	RPNCalc() {
+	}
+
+	void push(double n) {
+		stack.push(n);
+	}
+
+	double pop() {
+		if (stack.isEmpty()) {
+			return Double.NaN;
+		}
+		return stack.pop();
+	}
+
+	double peek(int i) {
+		int id = stack.size() - i;
+		if (id < 0 || id >= stack.size()) {
+			return Double.NaN;
+		}
+		return stack.get(id);
+	}
+
+	int getSize() {
+		return stack.size();
+	}
+
+	void performOperation(char c) {
+		if (stack.size() <= 1) {
+			return;
+		}
+		double a = stack.pop();
+		double b = stack.pop();
+		switch (c) {
+			case '+':
+				stack.push(a + b);
+				break;
+			case '-':
+				stack.push(a - b);
+				break;
+			case '*':
+				stack.push(a * b);
+				break;
+			case '/':
+				stack.push(a / b);
+				break;
+			default:
+				throw new IllegalArgumentException("Invalid operation");
+		}
+	}
+
+	@Override
+	public String toString() {
+		return stack.toString();
+	}
+}