Is there an easy way to evaluate String such as "81+23*5-21" in java?

Question

I'm trying to build a android calculator apps. I'll have some String such as "13+23-3" or "40*2+3". Is there a method can directly convert this kind of strings into double (with correct operator precedence)? Or i have to write a method myself?

I'd tried Double.parseDouble() and Double.valueOf() but both failed to convert it.

Or ... http://stackoverflow.com/questions/11302142/writing-string-evaluation-function?rq=1 — Brian Roach, Jul 05 '13 at 17:16

score 0 · Answer 1 · answered Jul 05 '13 at 17:14

You can use ScriptEngine class and use eval() function. I guess there may be a better way, but this will work, though not efficient certainly.

ScriptEngineManager m = new ScriptEngineManager();
ScriptEngine e = m.getEngineByName("js");        
Object result = e.eval("13+23-3");

Is there an easy way to evaluate String such as "81+23*5-21" in java?

1 Answers1