JAVA集合框架工具类自定义Collections集合方法

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 <Input>    collection对象类型   * @param <Output>    结果类型   * @return   */  public static <Input, Output> Output reduce(Collection<Input> original, Output initValue, ReduceFunction<Input, Output> 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 <Input>   * @param <Result>   */  public interface ReduceFunction<Input, Result> {    Result apply(Input input, Result lastResult);  }}

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<User> 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<User, BigDecimal>() {  @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<User, Integer>() {  @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 } }}