Builder允许我们通过使用将值传递给父类的内部构建器对象来清楚地分解对象构造
用一个内部类Builder来实现链式调用设置属性

public class BuilderTest {

  @Test
  public void test() {
    Programmer programmer = new Programmer.ProgrammerBuilder().setFirstName("F").setLastName("L")
            .setCity("City").setZipCode("0000A").setAddress("Street 39")
            .setLanguages(new String[] {"bash", "Perl"}).setProjects(new String[] {"Linux kernel"}).build();
    assertTrue("Programmer should be 'F L' but was '"+ programmer+"'", programmer.toString().equals("F L"));
  }

}

class Programmer {
  private String firstName;
  private String lastName;
  private String address;
  private String zipCode;
  private String city;
  private String[] languages;
  private String[] projects;

  private Programmer(String fName, String lName, String addr, String zip, String city, String[] langs, String[] projects) {
    this.firstName = fName;
    this.lastName = lName;
    this.address = addr;
    this.zipCode = zip;
    this.city = city;
    this.languages = langs;
    this.projects = projects;
  }

  public static class ProgrammerBuilder {
    private String firstName;
    private String lastName;
    private String address;
    private String zipCode;
    private String city;
    private String[] languages;
    private String[] projects;

    public ProgrammerBuilder setFirstName(String firstName) {
      this.firstName = firstName;
      return this;
    }

    public ProgrammerBuilder setLastName(String lastName) {
      this.lastName = lastName;
      return this;
    }

    public ProgrammerBuilder setAddress(String address) {
      this.address = address;
      return this;
    }

    public ProgrammerBuilder setZipCode(String zipCode) {
      this.zipCode = zipCode;
      return this;
    }

    public ProgrammerBuilder setCity(String city) {
      this.city = city;
      return this;
    }

    public ProgrammerBuilder setLanguages(String[] languages) {
      this.languages = languages;
      return this;
    }
    public ProgrammerBuilder setProjects(String[] projects) {
      this.projects = projects;
      return this;
    }

    public Programmer build() {
      return new Programmer(firstName, lastName, address, zipCode, city, languages, projects);
    }
  }

  @Override
  public String toString() {
    return this.firstName + " "+this.lastName;
  }

}