设计模式之建造者模式

建造者模式同样是创建型设计模式的一种，用于解决复杂对象的创建问题。
为什么需要建造者模式
为了得到一个对象，通常情况下我们调用构造方法然后再配合 set 方法做一些初始化工作即可。假定我们现在有一个传感器，传感器的名称和类型不能为空、客户ID可选、如果客户ID不为空时安装时间也不能为空，反应到类的代码如下。
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原文链接：https://blog.csdn.net/zzuhkp/article/details/11645641

public class Sensor {
    private String name;
    private String type;
    private Integer customerId;
    private Date installTime;
    private Double lower;
    private Double upper;
    public Sensor(String name, String type, Integer customerId, Date installTime, Double lower, Double upper) {
        ... 省略部分代码
        if ((lower != null && upper == null) || (upper != null && lower == null)) {
            throw new IllegalArgumentException("报警温度有误");
        }
        if (lower != null && upper != null && lower > upper) {
            throw new IllegalArgumentException("报警温度有误");
        }
        this.name = name;
        this.type = type;
        this.customerId = customerId;
        this.installTime = installTime;
        this.lower = lower;
        this.upper = upper;
    }
}

        Sensor sensor = new Sensor("温度传感器", "温度");
        sensor.setInstallTime(new Date());
        sensor.setCustomerId(1);

public class Sensor {
    private String name;
    private String type;
    private Integer customerId;
    private Date installTime;
    private Double lower;
    private Double upper;
    private Sensor(Build build) {
        this.name = build.name;
        this.type = build.type;
        this.customerId = build.customerId;
        this.installTime = build.installTime;
        this.lower = build.lower;
        this.upper = build.upper;
    }
    public static class Build {
        private String name;
        private String type;
        private Integer customerId;
        private Date installTime;
        private Double lower;
        private Double upper;
        public String getName() {
            return name;
        }
        public Build setName(String name) {
            this.name = name;
            return this;
        }
        public String getType() {
            return type;
        }
        public Build setType(String type) {
            this.type = type;
            return this;
        }
        public Integer getCustomerId() {
            return customerId;
        }
        public Build setCustomerId(Integer customerId) {
            this.customerId = customerId;
            return this;
        }
        public Date getInstallTime() {
            return installTime;
        }
        public Build setInstallTime(Date installTime) {
            this.installTime = installTime;
            return this;
        }
        public Double getLower() {
            return lower;
        }
        public Build setLower(Double lower) {
            this.lower = lower;
            return this;
        }
        public Double getUpper() {
            return upper;
        }
        public Build setUpper(Double upper) {
            this.upper = upper;
            return this;
        }
        public Sensor build() {
            if (this.name == null || this.name.isEmpty()) {
                throw new IllegalArgumentException("名称不能为空");
            }
            if (this.type == null || this.type.isEmpty()) {
                throw new IllegalArgumentException("类型不能为空");
            }
            if (this.customerId != null) {
                if (this.installTime != null && this.installTime.compareTo(new Date()) > 0) {
                    throw new IllegalArgumentException("安装时间有误");
                }
            }
            if ((this.lower != null && this.upper == null) || (this.upper != null && this.lower == null)) {
                throw new IllegalArgumentException("报警温度有误");
            }
            if (this.lower != null && this.upper != null && this.lower > this.upper) {
                throw new IllegalArgumentException("报警温度有误");
            }
            Sensor sensor = new Sensor(this);
            return sensor;
        }
    }
}

Sensor sensor = new Sensor.Build().setName("温度传感器").setType("温度").setCustomerId(1).setInstallTime(new Date()).build();