Detecting type of operator stored as string in java [duplicate]

Answer 1

You can convert the postfix expression into infix mathematical expression and execute it using expression evaluator in Java or javascript(not preferred). As you recommend java, following link will help you:

evaluating-a-math-expression-given-in-string-form

java-parse-a-mathematical-expression-given-as-a-string-and-return-a-number

Answer from above two links:

You can pass it to a BeanShell bsh.Interpreter, something like this:

Interpreter interpreter = new Interpreter(); 
interpreter.eval("result = 5+4*(7-15)");
System.out.println(interpreter.get("result"));

Let us know if your issue gets resolved.