Java Program to convert mathematical string to int

Java 8Object Oriented ProgrammingProgramming

To evaluate mathematical string to int, use Nashorn JavaScript in Java i.e. scripting. Nashorn invoke dynamics feature, introduced in Java 7 to improve performance.

For scripting, use the ScriptEngineManager class for the engine:

ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("nashorn");

Now, use put() to set a key/value pair in the state of the ScriptEngine:

scriptEngine.put("one", 10);
scriptEngine.put("two", 50);
scriptEngine.put("three", 40);

Now, here is the mathematical string. Use eval to evaluate:

String strExp = "(one + two - three) == 20";
Object evalExp = scriptEngine.eval(strExp);

Example

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
public class Demo {
   public static void main(String[] args) {
      ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
      ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("nashorn");
      scriptEngine.put("one", 10);
      scriptEngine.put("two", 50);
      scriptEngine.put("three", 40);
      try {
         String strExp = "(one + two - three) == 20";
         Object evalExp = scriptEngine.eval(strExp);
         System.out.println("Is "+strExp + " ? " + evalExp);
      } catch (ScriptException se) {
         se.printStackTrace();
      }
   }
}

Output

Is (one + two - three) == 20 ? true
raja
Published on 24-Apr-2019 12:16:42
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