JAVA集合框架工具类自定义Collections集合方法

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项目中有需要多次统计某些集合中的某个属性值，所以考虑封装一个方法，让其其定义实现计算方式。话不多说，看代码：

1、封装的自定义集合工具类：CollectionsCustom

 package com.test.util; import java.util.Collection; import org.apache.commons.collections.CollectionUtils; /** * 自定义集合处理类 */ public class CollectionsCustom { /** * 将传入的collection内对象进行计算后得出结果 * @param original    计算前collection * @param reduceFunction 计算方式 * @param initValue   计算结果初始值 * @param     collection对象类型 * @param     结果类型 * @return */ public static  Output reduce(Collection original, Output initValue, ReduceFunction reduceFunction) { Output result = initValue; if (CollectionUtils.isEmpty(original)) { return result; } if (reduceFunction == null) { return result; } for (Input input : original) { result = reduceFunction.apply(input, result); } return result; } /** * 自定义计算接口 * @param  * @param  */ public interface ReduceFunction { Result apply(Input input, Result lastResult); } }

2、测试类TestCollections

 package com.test; import java.math.BigDecimal; import java.util.Arrays; import java.util.List; import com.test.util.CollectionsCustom; public class TestCollection { private static List list = Arrays.asList( new User("张三", BigDecimal.valueOf(35.6), 18), new User("李四", BigDecimal.valueOf(85), 30), new User("赵六", BigDecimal.valueOf(66.55), 25)); public static void main(String[] args) { //统计集合内分数之和 testTotalScore(); //统计集合内年龄之和 testTotalAge(); } private static void testTotalScore(){ //统计集合内分数之和 BigDecimal totalScore = CollectionsCustom.reduce(list, BigDecimal.ZERO, new CollectionsCustom.ReduceFunction() { @Override public BigDecimal apply(User input, BigDecimal lastResult) { // TODO Auto-generated method stub return lastResult.add(input.getScore()); } }); System.out.println("总共分数：" + totalScore); } private static void testTotalAge(){ //统计集合内年龄之和 Integer totalAge = CollectionsCustom.reduce(list, 0, new CollectionsCustom.ReduceFunction() { @Override public Integer apply(User input, Integer lastResult) { // TODO Auto-generated method stub return lastResult += input.getAge(); } }); System.out.println("总共年龄：" + totalAge); } static class User{ private String userName; //姓名 private BigDecimal score;//分数 private Integer age; public String getUserName() { return userName; } public void setUserName(String userName) { this.userName = userName; } public BigDecimal getScore() { return score; } public void setScore(BigDecimal score) { this.score = score; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public User(String userName, BigDecimal score, Integer age) { super(); this.userName = userName; this.score = score; this.age = age; } public User() { // TODO Auto-generated constructor stub } } }

3、测试输出结果：