java Builder模式2

package com;

final class Computer {
    
    

    final String CPU;
    final String RAM;

    @Override
    public String toString() {
    
    
        return "Computer{" +
                "CPU='" + CPU + '\'' +
                ", RAM='" + RAM + '\'' +
                '}';
    }

    public Computer(Builder builder) {
    
    
        this.CPU = builder.CPU;
        this.RAM = builder.RAM;
    }

    public Builder newBuilder(){
    
    
        return new Builder(this);
    }

    public static final class Builder {
    
    
        String CPU;
        String RAM;

        public Builder() {
    
    
            this.CPU = "intel";
            this.RAM = "kingston";
        }

        public Builder(Computer computer){
    
    
            this.CPU = computer.CPU;
            this.RAM = computer.RAM;
        }

        public Builder CPU(String CPU) {
    
    
            this.CPU = CPU;
            return this;
        }

        public Builder RAM(String RAM) {
    
    
            this.RAM = RAM;
            return this;
        }

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

public class App2 {
    
    
    public static void main(String[] args) {
    
    
        Computer computer = new Computer.Builder().CPU("amd").build();
        System.out.println(computer);
        Computer computer2 = computer.newBuilder().RAM("kelvv").build();
        System.out.println(computer2);

    }
}

参考:
https://segmentfault.com/a/1190000017497699