How to evaluate a math expression given in string form?

java, math, string

Solution

With JDK1.6, you can use the built-in Javascript engine.

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

public class Test {
  public static void main(String[] args) throws ScriptException {
    ScriptEngineManager mgr = new ScriptEngineManager();
    ScriptEngine engine = mgr.getEngineByName("JavaScript");
    String foo = "40+2";
    System.out.println(engine.eval(foo));
    } 
}

Problem

I'm trying to write a Java routine to evaluate math expressions from `String` values like: - `"5+3"` - `"10-4*5"` - `"(1+10)*3"` I want to avoid a lot of if-then-else statements. How can I do this?

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