effective java（一）遇到多个构造器参数时要考虑用构建器

柔光的暖阳◎ 2022-09-25 14:21 126阅读 0赞

当一个类的变量比较多，构造函数也比较多，用重载构造函数的方法，会导致有客户端代码比较难维护，用这种Builder构造器来实现，扩展性好，便于维护。

/**
     * Created by wzj on 2016/9/11.
     */
    public class BuilderMode
    {
        private int id;
        private String name;
        private String age;
        private String score;
    
        public static class Builder
        {
            //初始化
            private final int id;
    
            private String name = "";
            private String age = "";
            private String score = "";
    
            //id是不能够改变的
            public Builder(final int id)
            {
                this.id = id;
            }
    
            public Builder name(final String name)
            {
                this.name = name;
                return this;
            }
    
            public Builder age(final String age)
            {
                this.age = age;
                return this;
            }
    
            public Builder score(final String score)
            {
                this.score = score;
                return this;
            }
    
            public BuilderMode build()
            {
                return new BuilderMode(this);
            }
        }
    
        //构造函数
        public BuilderMode(Builder builder)
        {
            this.id = builder.id;
            this.name = builder.name;
            this.age = builder.age;
            this.score = builder.score;
        }
    
        @Override
        public String toString()
        {
            return id + "--" + name + "--" + age + "--" + score;
        }
    
        public static void main(String[] args)
        {
            //构建对象
            BuilderMode.Builder builder = new BuilderMode.Builder(1001);
            BuilderMode builderMode = builder.name("wzj").age("23").score("100").build();
    
            System.out.println(builderMode.toString());
        }
    }