概述
使用private修饰构造器,使外部不能直接实例化Person对象.
通过静态工厂方法,获取一个Builder的实例.
通过Builder.build()方法发布Person对象.
代码演示
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public class {
private String name;
private int age;
private String sex;
private (PersonBuilder builder) {
this.name = builder.name;
this.age = builder.age;
this.sex = builder.sex;
}
public static Person2.PersonBuilder getBuilder() {
return new PersonBuilder();
}
private static class PersonBuilder {
private String name;
private int age;
private String sex;
public PersonBuilder name(String name) {
this.name = name;
return this;
}
public PersonBuilder age(int age) {
this.age = age;
return this;
}
public PersonBuilder sex(String sex) {
this.sex = sex;
return this;
}
public Person2 build() {
return new Person2(this);
}
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
public String getSex() {
return sex;
}
public String toString() {
return "Person2{" +
"name='" + name + ''' +
", age=" + age +
", sex='" + sex + ''' +
'}';
}
public static void main(String[] args) {
Person2 person2 = Person2.getBuilder()
.name("李四")
.age(10)
.sex("不确定")
.build();
System.out.println(person2);
}
}
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当前类如果出现多个线程共享同一个builder,可能会导致线程不安全,而每一次调用工厂方法都new一个builder对象又有点浪费,下面我们使用ThreadLocal类来改写上面的代码
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public class {
private static final ThreadLocal<PersonBuilder> builder = new ThreadLocal<PersonBuilder>() {
protected PersonBuilder initialValue() {
return new PersonBuilder();
}
};
private String name;
private int age;
private String sex;
private (PersonBuilder builder) {
this.name = builder.name;
this.age = builder.age;
this.sex = builder.sex;
}
public static Person2.PersonBuilder getBuilder() {
return builder.get();
}
private static class PersonBuilder {
private String name;
private int age;
private String sex;
public PersonBuilder name(String name) {
this.name = name;
return this;
}
public PersonBuilder age(int age) {
this.age = age;
return this;
}
public PersonBuilder sex(String sex) {
this.sex = sex;
return this;
}
public Person2 build() {
return new Person2(this);
}
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
public String getSex() {
return sex;
}
public String toString() {
return "Person2{" +
"name='" + name + ''' +
", age=" + age +
", sex='" + sex + ''' +
'}';
}
public static void main(String[] args) {
Person2 person2 = Person2.getBuilder()
.name("李四")
.age(10)
.sex("不确定")
.build();
System.out.println(person2);
}
}
|
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