import jdk.internal.org.objectweb.asm.ClassWriter;
import static jdk.internal.org.objectweb.asm.Opcodes.*;
public class HelloWorldGenerator {
public static void main(String[] args) throws Exception {
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
cw.visit(V1_8, ACC_PUBLIC, "HelloWorld", null, "java/lang/Object", null);
MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
mv.visitVarInsn(ALOAD, 0);
mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
mv.visitInsn(RETURN);
mv.visitMaxs(1, 1);
mv.visitEnd();
mv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "main", "([Ljava/lang/String;)V", null, null);
mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
mv.visitLdcInsn("Hello, world!");
mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
mv.visitInsn(RETURN);
mv.visitMaxs(2, 2);
mv.visitEnd();
cw.visitEnd();
byte[] code = cw.toByteArray();
ClassLoader classLoader = new ByteArrayClassLoader();
Class<?> clazz = classLoader.defineClass("HelloWorld", code);
Method method = clazz.getMethod("main", String[].class);
method.invoke(null, new Object[]{null});
}
static class ByteArrayClassLoader extends ClassLoader {
public Class<?> defineClass(String name, byte[] code) {
return defineClass(name, code, 0, code.length);
}
}
}
