Dead code without return sample.

Foo.java

import net.bytebuddy.asm.AsmVisitorWrapper;
import net.bytebuddy.description.method.MethodDescription;
import net.bytebuddy.description.type.TypeDescription;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

import static net.bytebuddy.matcher.ElementMatchers.named;

public class Foo {

    public static void main(String[] args) throws Exception {
        Class<?> type = new ByteBuddy()
                .redefine(Bar.class)
                .visit(new AsmVisitorWrapper.ForDeclaredMethods().method(named("bar"), new AsmVisitorWrapper.ForDeclaredMethods.MethodVisitorWrapper() {
                    @Override
                    public MethodVisitor wrap(TypeDescription instrumentedType,
                                              MethodDescription.InDefinedShape instrumentedMethod,
                                              MethodVisitor methodVisitor,
                                              final ClassFileVersion classFileVersion,
                                              int writerFlags,
                                              int readerFlags) {
                        return new MethodVisitor(Opcodes.ASM5, methodVisitor) {
                            @Override
                            public void visitLdcInsn(Object cst) {
                                if (cst.equals("foo")) { // Dummy check to see that the actual class was loaded.
                                    cst = "bar";
                                }
                                super.visitLdcInsn(cst);
                            }

                            @Override
                            public void visitInsn(int opcode) {
                                super.visitInsn(opcode);
                                if (opcode == Opcodes.RETURN) {
                                    mv.visitLdcInsn("qux");
                                    mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
                                }
                            }
                        };
                    }
                }))
                .make()
                .load(null)
                .getLoaded();
        type.getDeclaredMethod("bar").invoke(type.newInstance());
    }

    public static class Bar {

        public void bar() {
            System.out.println("foo");
        }
    }
}