Is it possible to evaluate a boolean expression for String comparions?

Question

I will have a String like

('abc' != 'xyz' AND 'thy' = 'thy') OR ('ujy' = 'ujy')

The String will be able to have as many "AND" groups as it wants. There will not be any nested groups within the AND groups. All groups will ALWAYS be serparated by an OR.

I can just switch out the AND for && and OR for ||.

What I would like is to pass this String into some type of eval method and output TRUE or FALSE.

Is there anything out there that can do this?

Answer 1

You can use the built-in Javascript engine coming with the JDK1.6 to evaluate string containing math expressions.

You an give a lookup here: ScriptEngine

Here an example:

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

public class Myclass {
    public static void main(String[] args) {

        try {

            ScriptEngineManager sem = new ScriptEngineManager();
            ScriptEngine se = sem.getEngineByName("JavaScript");
            String myExpression = "('abc' == 'xyz' && 'thy' == 'thy') || ('ujy' == 'ujy')";
            System.out.println(se.eval(myExpression));

        } catch (ScriptException e) {

            System.out.println("Invalid Expression");
            e.printStackTrace();

        }
    }
}

Just remember to replace the following:

'AND' with '&&',
'OR' with '||',
'=' must be '=='

Otherwise it will not accept your expression and will throws a javax.script.ScriptException