过滤器模式，获得元宇宙的一切事物

​ 今天带给大家的是过滤器模式，这个模式通俗易懂，我们直切正题！

​ 过滤器模式是一种结构型模式，这类模式更关注类和对象的组合。啥是过滤器模式呢，比如现在有一个动物类，这个动物类里面有猫、狗、狮子、猴子等等，那么你要怎么从里面过滤出狗的对象呢？你要怎么从里面过滤出即是公并且是狮子的对象呢？

​ 我们称一种过滤条件为一种标准，基于各种标准去过滤出你想要的对象列表，这一系列动作通过代码的方式实现解耦，我们叫做过滤器模式。

​ 现在举一个例子，现在有一个电脑类，这个电脑由很多零件组装而成，比如说cpu，内存条等等，我们现在按照我们想要的标准去过滤符合条件的电脑。

类图：

具体的代码实现：

public class Computer {
    // cpu型号
    private String cpuType;
    // 内存大小
    private int memorySize;
    // 操作系统类型
    private String operatingSystemType;

    public Computer(String cpuType, int memorySize, String operatingSystemType) {
        this.cpuType = cpuType;
        this.memorySize = memorySize;
        this.operatingSystemType = operatingSystemType;
    }

    public String getCpuType() {
        return cpuType;
    }

    public void setCpuType(String cpuType) {
        this.cpuType = cpuType;
    }

    public int getMemorySize() {
        return memorySize;
    }

    public void setMemorySize(int memorySize) {
        this.memorySize = memorySize;
    }

    public String getOperatingSystemType() {
        return operatingSystemType;
    }

    public void setOperatingSystemType(String operatingSystemType) {
        this.operatingSystemType = operatingSystemType;
    }

    @Override
    public String toString() {
        return "Computer{" +
                "cpuType='" + cpuType + '\'' +
                ", memorySize=" + memorySize +
                ", operatingSystemType='" + operatingSystemType + '\'' +
                '}';
    }
}

public interface Criteria {
    public List<Computer> meetCriteria(List<Computer> computerList);
}

public class CriteriaI5 implements Criteria {

    @Override
    public List<Computer> meetCriteria(List<Computer> computerList) {
        List<Computer> i5Computer = new ArrayList<>();
        for(Computer computer : computerList) {
            if(computer.getCpuType().equals("I5")) {
                i5Computer.add(computer);
            }
        }
        return i5Computer;
    }
}

public class Criteria8G implements Criteria {
    @Override
    public List<Computer> meetCriteria(List<Computer> computerList) {
        List<Computer> _8gComputer = new ArrayList<>();
        for(Computer computer : computerList) {
            if(computer.getMemorySize() == 8 * 1024) {
                _8gComputer.add(computer);
            }
        }
        return _8gComputer;
    }
}

public class AndCriteria implements Criteria {

    private Criteria criteria;
    private Criteria otherCriteria;

    public AndCriteria(Criteria criteria, Criteria otherCriteria) {
        this.criteria = criteria;
        this.otherCriteria = otherCriteria;
    }

    @Override
    public List<Computer> meetCriteria(List<Computer> computerList) {
        List<Computer> computers = criteria.meetCriteria(computerList);
        return otherCriteria.meetCriteria(computers);
    }
}

public class OrCriteria implements Criteria {

    private Criteria criteria;
    private Criteria otherCriteria;

    public OrCriteria(Criteria criteria, Criteria otherCriteria) {
        this.criteria = criteria;
        this.otherCriteria = otherCriteria;
    }

    @Override
    public List<Computer> meetCriteria(List<Computer> computerList) {
        List<Computer> computers1 = criteria.meetCriteria(computerList);
        List<Computer> computers2 = otherCriteria.meetCriteria(computerList);

        for(Computer computer : computers2) {
            if(!computers1.contains(computer)) {
                computers1.add(computer);
            }
        }
        return computers1;
    }
}

 public class Client {
    public static void main(String[] args) {
        List<Computer> computerList = new ArrayList<>();

        computerList.add(new Computer("I5", 1024, "Windows"));
        computerList.add(new Computer("I5", 1024 * 8, "Linux"));
        computerList.add(new Computer("I7", 1024 * 8, "Windows"));
        computerList.add(new Computer("I7", 1024, "Linux"));
        computerList.add(new Computer("I3", 1024 * 4, "Linux"));


        Criteria criteriaI5 = new CriteriaI5();
        Criteria criteria8G = new Criteria8G();
        Criteria criteriaI5Or8G = new OrCriteria(criteriaI5, criteria8G);
        Criteria criteriaI5And8G = new AndCriteria(criteriaI5, criteria8G);

        System.out.println("cpuType = I5----------------------------");
        printComputer(criteriaI5.meetCriteria(computerList));
        System.out.println("memorySize = 8G-------------------------");
        printComputer(criteria8G.meetCriteria(computerList));
        System.out.println("cpuType = I5 or memorySize = 8G---------");
        printComputer(criteriaI5Or8G.meetCriteria(computerList));
        System.out.println("cpuType = I5 and memorySize = 8G--------");
        printComputer(criteriaI5And8G.meetCriteria(computerList));
    }

    public static void printComputer(List<Computer> computers) {
        for(Computer computer : computers) {
            System.out.println(computer);
        }
    }
}
/*
cpuType = I5----------------------------
Computer{cpuType='I5', memorySize=1024, operatingSystemType='Windows'}
Computer{cpuType='I5', memorySize=8192, operatingSystemType='Linux'}
memorySize = 8G-------------------------
Computer{cpuType='I5', memorySize=8192, operatingSystemType='Linux'}
Computer{cpuType='I7', memorySize=8192, operatingSystemType='Windows'}
cpuType = I5 or memorySize = 8G---------
Computer{cpuType='I5', memorySize=1024, operatingSystemType='Windows'}
Computer{cpuType='I5', memorySize=8192, operatingSystemType='Linux'}
Computer{cpuType='I7', memorySize=8192, operatingSystemType='Windows'}
cpuType = I5 and memorySize = 8G--------
Computer{cpuType='I5', memorySize=8192, operatingSystemType='Linux'}
*/
复制代码

​ 好啦，本期如此简单，相信你一看就会！

​ 愿每个人都能带着怀疑的态度去阅读文章并探究其中原理。

道阻且长，往事作序，来日为章。

期待我们下一次相遇！