有人知道如何在Android Studio中使用Expression吗？

Question

I'm making a calculator in Android Studio and am facing a problem.

Here is my code:

String input = getinput();
try {
   if (!isEmpty() && !stateError) {
      if (input.contains("x")){
          input.replaceAll("x","*");
      }
      Expression expression = new ExpressionBuilder(input).build();
   }
} catch (Exception e) { }

When I type Expression , it shows the error:

"Cannot resolve symbol 'Expression'."

Is there any solution to solve this problem?

Answer 1

I don't know if you have found this or not, but there is this site that I found that seems to be the API for Expression and ExpressionBuilder called exp4j.

If that is in fact the API, then this is the download link for it.

---

Another way to evaluate an equation from a String in Java is to use the ScriptEngine interface along with the ScriptEngineManager class. You can use it like the following:

ScriptEngineManager mgr = new ScriptEngineManager();
ScriptEngine engine = mgr.getEngineByName("javascript");

try {
    String result = engine.eval(stringEquation).toString();
    System.out.println("Result: "+result);
} 
catch (ScriptException se) {
    // Handle error
}

• Java ScriptEngine doc
• Java ScriptEngineManager doc