1.使用场景：构造函数逻辑复杂，new对象成本高，提高性能。

如果一个类的构造方法为空，那么new这个类的对象成本很低，比clone()方法的成本低得多，但是如果这个类的构造方法稍微复杂一些（比如有两个参数赋值），那么clone()方法回避new这个类的对象性能高得多。

下面举个场景例子：
例如风控进件，有非常多的参数，但是进件对象需要经过多重规则引擎修改其中的变量值，但是我们还希望保留原始的进件参数，所以使用原型模式去复制对象，使用复制后的对象与规则引擎交互。

class RiskInputParam implements Cloneable{

    /**
     * 订单金额
     */
    private BigDecimal orderPrices;

    /**
     * 用户累计实物订单数
     */
    private Integer physicalOrdersNums;

    /**
     * 下单IP
     */
    private String ip;

    /**
     * 福卡激活时间
     */
    private Date fukaEnableTime;

    /**
     * 订单主单号
     */
    private String orderSn;

    /**
     * 订单主单号
     */
    private String mobile;

    /**
     * 下单手机号
     */
    private String orderMobile;

    /**
     * 订单类型：0普通实物 2手机充值 3卡券 4京东订单 5直冲 6美团 7集采订单 8春秋航空 9蛋糕叔叔 10高德打车 11裕福会员
     */
    private Integer orderType;

    /**
     * 订单主单号
     */
    private String rechargeMobile;

    /**
     * 订单主单号
     */
    private Integer differentMobileRechargeNum;

    /**
     * 手机号是否为虚拟号
     */
    private Integer virtualMobile;

    private int riskLevel;

    public RiskInputParam(BigDecimal orderPrices, Integer physicalOrdersNums, String ip, Date fukaEnableTime, String orderSn, String mobile, String orderMobile, Integer orderType, String rechargeMobile, Integer differentMobileRechargeNum, Integer virtualMobile) {
        this.orderPrices = orderPrices;
        this.physicalOrdersNums = physicalOrdersNums;
        this.ip = ip;
        this.fukaEnableTime = fukaEnableTime;
        this.orderSn = orderSn;
        this.mobile = mobile;
        this.orderMobile = orderMobile;
        this.orderType = orderType;
        this.rechargeMobile = rechargeMobile;
        this.differentMobileRechargeNum = differentMobileRechargeNum;
        this.virtualMobile = virtualMobile;
    }

    public int getRiskLevel() {
        return riskLevel;
    }

    public void setRiskLevel(int riskLevel) {
        this.riskLevel = riskLevel;
    }

    public RiskInputParam clone() throws CloneNotSupportedException{
        return (RiskInputParam) super.clone();
    }
}

class RuleEngine{
    public static RiskInputParam rule1(RiskInputParam riskInputParam){
        riskInputParam.setRiskLevel(1);
        return riskInputParam;
    }

    public static RiskInputParam rule2(RiskInputParam riskInputParam){
        riskInputParam.setRiskLevel(2);
        return riskInputParam;
    }
}


public class PrototypeMode {
    public static void main(String[] args) throws Exception{
        RiskInputParam riskInputParam = new RiskInputParam(new BigDecimal("20"),1,"111.111.111.111",new Date(),"S54325325235235","99999999","43434343434",1,"8888888888",1,1);
        long time1 = System.nanoTime();
        RiskInputParam riskInputParam2 = new RiskInputParam(new BigDecimal("20"),1,"111.111.111.111",new Date(),"S54325325235235","99999999","43434343434",1,"8888888888",1,1);
        RiskInputParam riskInputParam3 = new RiskInputParam(new BigDecimal("20"),1,"111.111.111.111",new Date(),"S54325325235235","99999999","43434343434",1,"8888888888",1,1);
        RiskInputParam riskInputParam4 = new RiskInputParam(new BigDecimal("20"),1,"111.111.111.111",new Date(),"S54325325235235","99999999","43434343434",1,"8888888888",1,1);
        RiskInputParam riskInputParam5 = new RiskInputParam(new BigDecimal("20"),1,"111.111.111.111",new Date(),"S54325325235235","99999999","43434343434",1,"8888888888",1,1);
        long time2 = System.nanoTime();
        RuleEngine.rule1(riskInputParam);
        RuleEngine.rule2(riskInputParam2);
        System.out.println("初始化所需时间："+(time2-time1));


        long time4 = System.nanoTime();
        RiskInputParam clone = riskInputParam.clone();
        RiskInputParam clone2 = riskInputParam.clone();
        RiskInputParam clone3 = riskInputParam.clone();
        RiskInputParam clone4 = riskInputParam.clone();
        RiskInputParam clone5 = riskInputParam.clone();
        long time5 = System.nanoTime();
        RuleEngine.rule1(riskInputParam);
        RuleEngine.rule2(clone);
        System.out.println("使用原型模式初始化所需时间："+(time5-time4));

    }
}
初始化所需时间：16795
使用原型模式初始化所需时间：12596

这里通过构造函数创建了5个对象，与调用clone()浅克隆出5个对象，每次都是浅克隆用时少。