android string equation to java code

Question

How could I parse a string statement into code?

e.g.:

    boolean isOnline = true;
    boolean isConnected = true;
    String statement = "isOnline && isConnected";

    if(statement) // do something

It's really not clear what you're asking here. Are you asking how to evaluate a SQLite expression in Java? — Codeman, Apr 12 '13 at 23:19
no just asking how would you translate a string equation to java code like i wrote up there. — anonimoo90, Apr 12 '13 at 23:32
@anonimoo90 you want to evaluate the *statement* that you stored in your String? — Lukas Knuth, Apr 12 '13 at 23:35
there's nothing built in to Java to do that. You're looking for a parser, which is not a trivial project. — Codeman, Apr 12 '13 at 23:36

Ilya Gazman · Answer 1 · 2013-04-13T18:30:15.740

0

try this:

   boolean isOnline = true;
   boolean isConnected = true;
   String statement = "isOnline && isConnected";
   String[] split = statement .split(" && ");

   if(split.lenght > split[0].equals("isOnline") && split[1].equals("isConnected")){
       // do something
   }

edited Apr 13 '13 at 18:30

answered Apr 13 '13 at 08:07

Ilya Gazman

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And how would this handle variable names and expressions, like in the question? – CL. Apr 13 '13 at 08:13
sorry this doesnt work for me, like i said i will type variable names in string format and need the string to run as an statement like in the example i gave – anonimoo90 Apr 13 '13 at 17:55
@anonimoo90 how about now? – Ilya Gazman Apr 13 '13 at 18:30

score 0 · Answer 2 · edited May 23 '17 at 11:43

I would suggest the following strategy depending your knowledge on how is structured your string expression.

1- Develop your own parser.

You will have to develop your own grammar. There is an ANTLR port on android : ANTLR and Android

Ie, you will get with your expression ("isOnline" && "isConnected")

2- Use reflexivity/introspection

Once the string is parsed, you could use reflexivity to translate field or method expression into a field or a method.

Ie, you will translate "isOnline" to isOnline and "isConnected" to isConnected

Good luck for this

score 0 · Answer 3 · edited May 23 '17 at 12:12

The original Java has a built-in JavaCompiler class which would allow you to compile and load code that forms a complete valid .java file.

Android does not have this.

You could try to use some JavaScript engine written in Java (see, e.g., Android utilize V8 without WebView).

However, this would still not allow you to access local variables declared in your Java function. (With the reflection API, you would be able to read the values of class fields.)

android string equation to java code

3 Answers3