Test.java

import static com.google.common.base.Preconditions.checkArgument;

public class MyObject {
  public final String name;
  public final String wat;

  private MyObject(String name, String wat) {
    this.name = name;
    this.wat = wat;
  }

  public static BuildName newBuilder() {
    return new Builder();
  }

  public interface BuildObj {
    MyObject build();
  }

  public interface BuildName {
    BuildWat setName(String name);
  }

  public interface BuildWat {
    BuildObj setWat(String name);
  }

  public static class Builder implements BuildWat, BuildName, BuildObj {
    private String name;
    private String wat;

    private Builder() {}

    public BuildWat setName(String name) {
      checkArgument(name != null);
      this.name = name;
      return this;
    }

    public BuildObj setWat(String wat) {
      checkArgument(wat != null);
      this.wat = wat;
      return this;
    }

    public MyObject build() {
      return new MyObject(name, wat);
    }
  }
}