How to Execute Java Code from a String Variable?

Dynamic Code Execution from String in Java

This article delves into the inquiry of executing a piece of Java code stored within a String variable. Can this code be transformed into a Java statement and executed dynamically?

Dynamic Code Compilation and Execution

One approach to tackle this problem involves utilizing Java's Compiler API. This allows you to compile Java code on the fly. Here's a brief overview of the steps involved:

• Compile the code contained in the String using a JavaCompiler instance.
• Obtain a ClassLoader instance to load the compiled class.
• Create an instance of the dynamically loaded class and invoke its methods.

Alternative: Beanshell

Alternatively, you can consider using the Beanshell interpreted scripting language. Beanshell offers a seamless interface for executing Java code from strings. Here's how you can use Beanshell:

• Import the Beanshell library into your project.
• Create an instance of the Interpreter class and provide the Java code String as input.
• Execute the code by calling the eval() method.

Implementation Details

The following code snippet demonstrates the dynamic execution of Java code using Beanshell:

<code class="java">import bsh.Interpreter;

public class DynamicCodeExecution {

    public static void main(String[] args) throws Exception {
        // Java code stored in a String
        String javaCode = "if(polishScreenHeight >= 200 && " +
            "polishScreenHeight <= 235 && polishScreenWidth >= 220) { }";

        // Create Beanshell interpreter
        Interpreter interpreter = new Interpreter();

        // Set the code to be executed
        interpreter.eval(javaCode);
    }
}</code>

Using this approach, the Java code within the String will be dynamically executed, allowing you to evaluate conditions or perform operations at runtime.

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