code updated

src/xs_ibdpcompsci_javaintro/practice1.java

@@ -0,0 +1,66 @@
+package xs_ibdpcompsci_javaintro;
+import java.util.*;
+
+class RPN_Calculator {
+    static ArrayList<Object> request_input() {
+		Scanner input = new Scanner(System.in);
+		
+		// Initialize variables. 
+		ArrayList<Object> USER_INPUTS = new ArrayList<Object>();
+		String USER_INPUT_CURRENT = "";
+		Boolean USER_INPUT_MORE = true;
+		
+		// Loop for input. 
+		do {
+			USER_INPUT_CURRENT = input.nextLine();
+
+			if (USER_INPUT_CURRENT.isEmpty() || USER_INPUT_CURRENT.isBlank()) {
+				USER_INPUT_MORE = false;
+			} else if (USER_INPUT_CURRENT.matches("-?\\d+(\\.\\d+)?")) {
+				USER_INPUTS.add(Float.parseFloat(USER_INPUT_CURRENT));
+			} else {
+				if (USER_INPUT_CURRENT.matches("[+\\-*\\/^]") && (USER_INPUTS.size() > 2)) {
+					USER_INPUTS.add(USER_INPUT_CURRENT);
+				} else if (USER_INPUT_CURRENT.toLowerCase() == "exit") {
+					System.exit(0);
+				} else {
+					// The user inputs a wrong code. Let the user edit it. 
+					System.out.println("\\033[A");
+				};
+			};
+		} while (USER_INPUT_MORE == true);
+
+		input.close();
+		return (USER_INPUTS);
+	}
+	
+	static float calculate(ArrayList<Object> ENTRIES_LIST, String OPERATION) {
+		// Calculate length. 
+		int ENTRIES_LIST_LENGTH = ENTRIES_LIST.size();
+
+		float OPERATION_RESULT = (float) ENTRIES_LIST.get(0);
+
+		if (ENTRIES_LIST_LENGTH > 1) {
+			for (int ENTRY_CURRENT = 1; ENTRY_CURRENT < ENTRIES_LIST_LENGTH; ENTRY_CURRENT++) {
+				if (OPERATION == "+") {
+					OPERATION_RESULT += (float) ENTRIES_LIST.get(ENTRY_CURRENT);
+				} else if (OPERATION == "-") {
+					OPERATION_RESULT -= (float) ENTRIES_LIST.get(ENTRY_CURRENT);
+				};
+			};
+		};
+
+		return (OPERATION_RESULT);
+	};
+	
+	
+	public static void main(String[] args) {
+		// Initialize the input numbers. 
+		ArrayList<Object> NUMBERS_INPUT = new ArrayList<Object>();
+		while (true) {
+			NUMBERS_INPUT = request_input();
+			
+
+		}
+    }
+}