在 Java 中为类编写构建器时出现问题

问题描述

我在用 Java 为类编写构建器时遇到问题。它总是给我一个错误，说找不到符号。

class Company {
    private String name;
    private String address;
    private String contact;
    private int sizeOfEmployee;
    private Date createdTime;
  
    @Override
    public String toString() {
        return "Company{" +
                "name='" + name + '\'' +
                ",address='" + address + '\'' +
                ",contact='" + contact + '\'' +
                ",sizeOfEmployee=" + sizeOfEmployee +
                ",createdTime=" + createdTime +
                '}';
    }
   
   public static class builder {
    private String name;
    private String address;
    private String contact;
    private int sizeOfEmployee;
    private Date createdTime;
    
    
   public builder Name (String name){
     this.name = name;
     return this;
   }
    public builder address(String address){
     this.address = address;
     return this;
   }
   
    public builder contact(String contact){
     this.contact = contact;
     return this;
   }
    public builder size(int sizeOfEmployee){
     this.sizeOfEmployee = sizeOfEmployee;
     return this;
   }
    public builder date(Date createdTime){
     this.createdTime = createdTime;
     return this;
   }
   
   }
   
     
}

我想编写一个可以打印出我的 Company 类的构建器。谁能告诉我为什么我的建造者不工作？我搜索如何编写构建器并尝试复制该方法。但它在这里不起作用。它给了我一个错误，说错误找不到符号。如果我打电话

Company abc = Company.builder().name("abc").address("Virginia").createdTime(new Date()).sizeOfEmployee(300).contact("12345").build();

它会打印出来

Company{name='abc',address='Virginia',contact='12345',sizeOfEmployee=300,createdTime=Wed Oct 21 11:50:41 EDT 2020}

解决方法

您正在调用不存在的静态方法构建器“Company.builder()”。你可以这样解决问题：

public class Company {
    private String name;
    private String address;

    public static CompanyBuilder builder() {
        return new CompanyBuilder();
    }
    private static class CompanyBuilder {
        private final Company company = new Company();
        public CompanyBuilder name(String name){
            company.name = name;
            return this;
        }
        public CompanyBuilder address(String address){
            company.address = address;
            return this;
        }
        public Company build() {
            return company;
        }
    }
    public static void main(String[] args) {
        System.out.println(Company.builder().name("name").address("address").build());
    }
}

我建议将 Lombok 用于 Java 项目。使用包含 Lombok 插件和依赖项的一个注解 @Builder，您可以解决问题，您还可以使用许多功能而不是样板代码。

import lombok.Builder;
import lombok.ToString;

@Builder
@ToString
public class Company {
    private String name;
    private String address;

    public static void main(String[] args) {
        System.out.println(Company.builder().name("name").address("address").build());
    }
}

builder class class class java java