Generating generic fields with JCodeModel: https://blog.jensknipper.de/blog/dealing-with-generic-fields-in-jcodemodel/

GenericFieldGenerator.java

package de.jensknipper.jcodemodel;

import com.helger.jcodemodel.*;

import java.io.File;
import java.io.IOException;
import java.util.*;

public class GenericFieldGenerator {

    public static void main(String[] args) throws JCodeModelException, IOException {

        JCodeModel codeModel = new JCodeModel();

        JPackage jPackage = codeModel._package("de.jensknipper.jcodemodel");
        JDefinedClass jClass = jPackage._class("ExampleClassName");
        // JDefinedClass jClass = codeModel._class("ExampleClassName"); // Alternative without package declaration
        
        JTypeWildcard wildcard = codeModel.ref(Comparable.class).wildcard(EWildcardBoundMode.EXTENDS);
        AbstractJClass classType = codeModel
                .ref(Map.class)
                .narrow(
                        codeModel.ref(String.class),
                        codeModel.ref(List.class).narrow(wildcard));

        JFieldVar field = jClass.field(JMod.PRIVATE + JMod.STATIC + JMod.FINAL, classType, "exampleField");

        field.init(codeModel.ref(HashMap.class).narrow(Collections.emptyList())._new());

        File file = new File("src/main/java");
        codeModel.build(file);
    }
}