1 问题

建造者模式，我们也许不陌生，因为我们看到很多开源框架或者Android源码里面用到，类似这样的代码结构

A a = new A.builder().method1("111").method2("222").build();

很明显，一般这里的结构有builder()构造函数，还有build()函数，主要用来干嘛呢？还不是为了构建对象，如果需要设置的参数很多的话，一个一个去set很繁琐也不好看，下面有个例子简单粗暴展示。 

 

 

 

 

 

 

 

 

2 测试代码实现

package com.example.test1;public class Student {private int id;private String name;private int age;private String classNmae;public Student(Builder builder) {this.id = builder.id;this.name = builder.name;this.age = builder.age;this.classNmae = builder.classNmae;}public int getId() {return id;}public String getName() {return name;}public int getAge() {return age;}public String getClassNmae() {return classNmae;}@Overridepublic String toString() {return "Student{" +"id=" + id +", name='" + name + '\'' +", age=" + age +", classNmae='" + classNmae + '\'' +'}';}public static class Builder {private int id;private String name;private int age;private String classNmae;public Builder() {}public Builder id(int id) {this.id = id;return this;}public Builder name(String name) {this.name = name;return this;}public Builder age(int age) {this.age = age;return this;}public Builder className(String classNmae) {this.classNmae = classNmae;return this;}public Student build() {return new Student(this);}}
}

                Student student = new Student.Builder().name("chenyu").age(28).id(1).className("erzhong").build();Log.i(TAG, "student toString is:" + student.toString());

 

 

 

 

 

 

 

 

3 运行结果

18376-18376/com.example.test1 I/chenyu: student toString is:Student{id=1, name='chenyu', age=28, classNmae='erzhong'}

 

 

 

 

 

 

 

4 总结

1）我们需要构建一个对象很多参数的时候用这种方式

2）最关键的是需要构建的对象类里面有个Builder类作为参数传递

    public Student(Builder builder) {this.id = builder.id;this.name = builder.name;this.age = builder.age;this.classNmae = builder.classNmae;}

3）最后build()函数里面返回的是需要构建的类本身

        public Student build() {return new Student(this);}