过滤器模式

有啥用？

就是从一大堆对象中筛选出符合条件的对象来，就这么简单。

类图

类图.png

输出

All objects:
condition 2 : 466002798
condition 2 : 1784662007
condition 0 : 997110508
condition 0 : 509886383
condition 1 : 1854778591
condition 2 : 2054798982
condition 2 : 885951223
condition 0 : 191382150
condition 0 : 142666848
condition 2 : 1060830840

condition 0 : 997110508
condition 0 : 509886383
condition 0 : 191382150
condition 0 : 142666848

condition 1 : 1854778591

condition 2 : 466002798
condition 2 : 1784662007
condition 2 : 2054798982
condition 2 : 885951223
condition 2 : 1060830840

Process finished with exit code 0

调用

package com.company;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class Main {

    public static void main(String[] args) {
    // write your code here
        int objectSum = 10;
        List<TargetClass> sourceList = new ArrayList<>();
        System.out.println("All objects:");
        for (int couter = 0;couter < objectSum;couter++) {
            TargetClass tempObject = new TargetClass();
            tempObject.objectIndex = new Random().nextInt(3);
            System.out.println("condition " + tempObject.objectIndex + " : " +tempObject.hashCode());
            sourceList.add(tempObject);
        }
        System.out.println();

        List<TargetClass> resultList0 = new FirstConditionFilter().filterSourceObjectsList(sourceList);
        for (TargetClass iterator : resultList0) {
            System.out.println("condition 0 : " + iterator.hashCode());
        }
        System.out.println();

        List<TargetClass> resultList1 = new SecondConditionFilter().filterSourceObjectsList(sourceList);
        for (TargetClass iterator : resultList1) {
            System.out.println("condition 1 : " + iterator.hashCode());
        }
        System.out.println();

        List<TargetClass> resultList2 = new ThirdConditionFilter().filterSourceObjectsList(sourceList);
        for (TargetClass iterator : resultList2) {
            System.out.println("condition 2 : " + iterator.hashCode());
        }
    }
}

被依赖的对象类型

package com.company;

public class TargetClass {
    public int objectIndex;
}

过滤器接口

package com.company;

import java.util.List;

public interface FilterInterface {
    List<TargetClass> filterSourceObjectsList(List<TargetClass> sourceList);
}

过滤器0

package com.company;

import java.util.ArrayList;
import java.util.List;

public class FirstConditionFilter implements FilterInterface {
    @Override
    public List<TargetClass> filterSourceObjectsList(List<TargetClass> sourceList) {
        List<TargetClass> resultList = new ArrayList<>();
        for (TargetClass iterator:sourceList) {
            if (iterator.objectIndex == 0)resultList.add(iterator);
        }
        return resultList;
    }
}

过滤器1

package com.company;

import java.util.ArrayList;
import java.util.List;

public class SecondConditionFilter implements FilterInterface {
    @Override
    public List<TargetClass> filterSourceObjectsList(List<TargetClass> sourceList) {
        List<TargetClass> resultList = new ArrayList<>();
        for (TargetClass iterator:sourceList) {
            if (iterator.objectIndex == 1)resultList.add(iterator);
        }
        return resultList;
    }
}

过滤器2

package com.company;

import java.util.ArrayList;
import java.util.List;

public class ThirdConditionFilter implements FilterInterface {
    @Override
    public List<TargetClass> filterSourceObjectsList(List<TargetClass> sourceList) {
        List<TargetClass> resultList = new ArrayList<>();
        for (TargetClass iterator:sourceList) {
            if (iterator.objectIndex == 2)resultList.add(iterator);
        }
        return resultList;
    }
}

多谢捧场

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