Java.lang.Compiler class in Java

In this tutorial, we will learn about the Compiler class in Java. This class provides support and related services to java-to-native-code compilers.

Declaration

The declaration of java.lang.compiler class is as follows:

public final class Compiler 
 extends Object

Methods

The Compiler class has the following methods:

command(): This method tests the argument type and performs documented operations. The syntax for java.lang.Compiler.command() as follows:

public static boolean command(Object arg)

Here, arg is a compiler-specific argument. The method returns a compiler-specific value and throws a NullPointerException if arg is null.

compileClass():  This method compiles the class passed as the argument. The syntax is as follows:

public static boolean compileClass(Class cl)

Here, cl is the class that is to be compiled.  The method returns true if compilation is successful, otherwise false. A NullPointerException is thrown if cl is null.

compileClasses(): This method compiles all the classes that have the same name as the string passed as argument. See the syntax.

public static boolean compileClasses(String s)

Here, compileClasses() takes a string argument and compiles all the classes with the same name as s. On successful compilation, it returns true, or else it returns false. The method throws a NullPointerException if s is null.

enable(): This method causes the compiler to start or resume operation. The syntax is as follows:

public static void enable()

The function takes no parameter and does not return anything.

disable(): This method stops the compiler to perform operations. The syntax is given is as follows:

public static void disable()

The function takes no parameter and does not return anything.

Have a look at the Java program below to understand the working of the above-explained methods.

import java.lang.*;

public class Main{
    
    public static class ExampleClass{
        public ExampleClass()
        {
            
        }
    }
    
    public static void main(String args[])
    {
        ExampleClass ex = new ExampleClass();
        
        Compiler.enable();
        
        Class cl = ex.getClass();
        System.out.println(cl);
        
        Object obj = Compiler.command("javac ExampleClass");
        System.out.println(obj);
        
        boolean compiled = Compiler.compileClass(cl);
        if(compiled == true)
        {
            System.out.println("Compilation Successful using compileClass() method.");
        }
        else
        {
            System.out.println("Compilation unsuccessful using compileClass() method.");
        }
        
        String str = "ExampleClass";
        boolean compiled_again = Compiler.compileClasses(str);
        if(compiled_again == true)
        {
            System.out.println("Compilation Successful using compileClasses() method.");
        }
        else
        {
            System.out.println("Compilation unsuccessful using compileClasses() method.");
        }
        
        Compiler.disable();
    }
}

Output:

class Main$ExampleClass
null
Compilation unsuccessful using compileClass() method.
Compilation unsuccessful using compileClasses() method.

Also read: How to create object of a Java class?