import java.util.List; public class SuperBuilderBasicToBuilder { public static class Parent { int field1; List items; @java.lang.SuppressWarnings("all") public static abstract class ParentBuilder> { @java.lang.SuppressWarnings("all") private int field1; @java.lang.SuppressWarnings("all") private java.util.ArrayList items; @java.lang.SuppressWarnings("all") protected B $fillValuesFrom(final C instance) { this.field1(instance.field1); this.items(instance.items == null ? java.util.Collections.emptyList() : instance.items); return self(); } @java.lang.SuppressWarnings("all") protected abstract B self(); @java.lang.SuppressWarnings("all") public abstract C build(); @java.lang.SuppressWarnings("all") public B field1(final int field1) { this.field1 = field1; return self(); } @java.lang.SuppressWarnings("all") public B item(final String item) { if (this.items == null) this.items = new java.util.ArrayList(); this.items.add(item); return self(); } @java.lang.SuppressWarnings("all") public B items(final java.util.Collection items) { if (this.items == null) this.items = new java.util.ArrayList(); this.items.addAll(items); return self(); } @java.lang.SuppressWarnings("all") public B clearItems() { if (this.items != null) this.items.clear(); return self(); } @java.lang.Override @java.lang.SuppressWarnings("all") public java.lang.String toString() { return "SuperBuilderBasicToBuilder.Parent.ParentBuilder(field1=" + this.field1 + ", items=" + this.items + ")"; } } @java.lang.SuppressWarnings("all") private static final class ParentBuilderImpl extends ParentBuilder { @java.lang.SuppressWarnings("all") private ParentBuilderImpl() { } @java.lang.Override @java.lang.SuppressWarnings("all") protected ParentBuilderImpl self() { return this; } @java.lang.Override @java.lang.SuppressWarnings("all") public Parent build() { return new Parent(this); } } @java.lang.SuppressWarnings("all") protected Parent(final ParentBuilder b) { this.field1 = b.field1; java.util.List items; switch (b.items == null ? 0 : b.items.size()) { case 0: items = java.util.Collections.emptyList(); break; case 1: items = java.util.Collections.singletonList(b.items.get(0)); break; default: items = java.util.Collections.unmodifiableList(new java.util.ArrayList(b.items)); } this.items = items; } @java.lang.SuppressWarnings("all") public static ParentBuilder builder() { return new ParentBuilderImpl(); } @java.lang.SuppressWarnings("all") public ParentBuilder toBuilder() { return new ParentBuilderImpl().$fillValuesFrom(this); } } public static class Child extends Parent { double field3; @java.lang.SuppressWarnings("all") public static abstract class ChildBuilder> extends Parent.ParentBuilder { @java.lang.SuppressWarnings("all") private double field3; @java.lang.Override @java.lang.SuppressWarnings("all") protected B $fillValuesFrom(final C instance) { super.$fillValuesFrom(instance); this.field3(instance.field3); return self(); } @java.lang.Override @java.lang.SuppressWarnings("all") protected abstract B self(); @java.lang.Override @java.lang.SuppressWarnings("all") public abstract C build(); @java.lang.SuppressWarnings("all") public B field3(final double field3) { this.field3 = field3; return self(); } @java.lang.Override @java.lang.SuppressWarnings("all") public java.lang.String toString() { return "SuperBuilderBasicToBuilder.Child.ChildBuilder(super=" + super.toString() + ", field3=" + this.field3 + ")"; } } @java.lang.SuppressWarnings("all") private static final class ChildBuilderImpl extends ChildBuilder { @java.lang.SuppressWarnings("all") private ChildBuilderImpl() { } @java.lang.Override @java.lang.SuppressWarnings("all") protected ChildBuilderImpl self() { return this; } @java.lang.Override @java.lang.SuppressWarnings("all") public Child build() { return new Child(this); } } @java.lang.SuppressWarnings("all") protected Child(final ChildBuilder b) { super(b); this.field3 = b.field3; } @java.lang.SuppressWarnings("all") public static ChildBuilder builder() { return new ChildBuilderImpl(); } @java.lang.SuppressWarnings("all") public ChildBuilder toBuilder() { return new ChildBuilderImpl().$fillValuesFrom(this); } } public static void test() { Child x = Child.builder().field3(0.0).field1(5).item("").build().toBuilder().build(); } }