How to parse a mathematical expression given as a string and return a number? [duplicate]

Answer 1

You can use the ScriptEngine class and evaluate it as a javascript string

ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("js");        
Object result = engine.eval("5+4*(7-15)");

Indeed , yu should know that the result of the following instruction in javascript :

   eval('var aa=5+4*(7-15)')
   aa // -27

There may be a better way, but this one works.