create expression designer in java

I'm trying to create a expression designer in Java, any idea if there are something like that in the market? The expression that i need to build are like this:

1. Var >= 5 Or Var = null
2. Var2 > 20 开发者_运维知识库And Var2 < 50
3. Var3 = 15

How can i do this?

Thanks.

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Is this what you need?

if (Var >= 5 || var == null)
  if (Var2 > 20 && Var2<50)
     Var3 = 15;

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I doubt there is any out-of-the-box tool that lets you define your own expression language (or do you have a specific language in mind?) and provides you a generic GUI for that.