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; } @Override public 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
1. public Student build() { 2. return new Student(this); 3. }
