類圖

原始碼

package com.bulid;

public class Computer {

    private String cpu;//必須
    private String ram;//必須
    private int usbCount;//可選
    private String keyboard;//可選
    private String display;//可選

    private Computer(Builder builder) {
        this.cpu = builder.cpu;
        this.ram = builder.ram;
        
 
this.usbCount = builder.usbCount;
        this.keyboard = builder.keyboard;
        this.display = builder.display;
    }

    public static class Builder {
        private String cpu;//必須
        private String ram;//必須
        private int usbCount;//可選
        private String keyboard;//可選
        private String display;//
 
可選

        public Builder(String cpu, String ram) {
            this.cpu = cpu;
            this.ram = ram;
        }

        public Builder setUsbCount(int usbCount) {
            this.usbCount = usbCount;
            return this;
        }

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

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

        public Computer builder() {

            return new Computer(this);
        }

    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("Computer{");
        sb.append("cpu='").append(cpu).append('\'');
        sb.append(", ram='").append(ram).append('\'');
        sb.append(", usbCount=").append(usbCount);
        sb.append(", keyboard='").append(keyboard).append('\'');
        sb.append(", display='").append(display).append('\'');
        sb.append('}');
        return sb.toString();
    }
public static void main(String[] args) {
    // 建造正模式
    Computer computer = new Computer.Builder("因特爾", "三星")
            .setDisplay("三星24寸")
            .setKeyboard("羅技")
            .setUsbCount(2)
            .builder();
    System.out.println(computer);
}
}

測試截圖