快捷導(dǎo)航

Java如何根據(jù)實(shí)體指定字段值對其List進(jìn)行排序詳解

更新時(shí)間：2024年07月02日 09:56:08 作者：熙子XIZI

在Java項(xiàng)目中可能會(huì)遇到給出一些條件,將List元素按照給定條件進(jìn)行排序的情況,這篇文章主要給大家介紹了關(guān)于Java如何根據(jù)實(shí)體指定字段值對其List進(jìn)行排序的相關(guān)資料,文中通過代碼介紹的非常詳細(xì),需要的朋友可以參考下

一、先準(zhǔn)備個(gè)實(shí)體PO

public class Student {
    private String name;
    private String age;
    private String score;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getAge() {
        return age;
    }
    public void setAge(String age) {
        this.age = age;
    }
    public String getScore() {
        return score;
    }
    public void setScore(String score) {
        this.score = score;
    }
}

二、簡易版本，利用比較器來實(shí)現(xiàn)排序

public class SortUtil {
    public static void main(String[] args) {
        List<Student> students = new ArrayList<>();
        Student studentA = new Student();
        studentA.setName("a");
        studentA.setAge("16");
        studentA.setScore("95");
        Student studentB = new Student();
        studentB.setName("b");
        studentB.setAge("16");
        studentB.setScore("83");
        Student studentC = new Student();
        studentC.setName("c");
        studentC.setAge("16");
        studentC.setScore("90");

        students.add(studentA);
        students.add(studentB);
        students.add(studentC);

        System.out.println("-----排序前----");
        for (Student student : students) {
            System.out.println("學(xué)生：" + student.getName() + "的分?jǐn)?shù)為[" + student.getScore() + "]");
        }
        System.out.println();


        //排序-------------比較器來實(shí)現(xiàn)排序
        Collections.sort(students, new Comparator<Student>() {
            @Override
            public int compare(Student o1, Student o2) {
                BigDecimal data1 = new BigDecimal(o1.getScore());
                BigDecimal data2 = new BigDecimal(o2.getScore());
                return data2.compareTo(data1);
            }
        });
        //------------------------------

        System.out.println("-----排序后----");
        for (Student student : students) {
            System.out.println("學(xué)生：" + student.getName() + "的分?jǐn)?shù)為[" + student.getScore() + "]");
        }

    }

測試結(jié)果：

三、封裝成通用的方法類調(diào)用

import java.lang.reflect.Field;
import java.math.BigDecimal;
import java.util.*;

/**
 * @ClassName: SortUtil
 * @Author: XIZI
 * @Description: 排序
 */
public class SortUtil {
	private static Logger logger = Logger.getLogger(SortUtil.class);

    /**
     * 排序
     *
     * @param list      需要排序的list
     * @param filedName 字段名
     * @param ascFlag   是否升序
     * @param clazz     排序的類
     * @param <T>
     */
    public static <T> void sort(List<T> list, String filedName, boolean ascFlag, Class<T> clazz) {
        //通過比較器來實(shí)現(xiàn)排序
        list.sort(new Comparator<T>() {

            @Override
            public int compare(T o1, T o2) {
                String data1s = "";
                String data2s = "";

                Field[] fields = getAllFields(clazz);

                for (Field field : fields) {
                    // 設(shè)置字段可訪問（必須，否則報(bào)錯(cuò)）
                    field.setAccessible(true);
                    if (field.getName().equals(filedName)) {
                        try {
                            data1s =  field.get(o1).toString();
                            data2s =  field.get(o2).toString();

                        } catch (IllegalAccessException e) {
                            logger.error("排序出現(xiàn)異常：", e);
                            return 0;
                        }
                        break;
                    }
                }
                BigDecimal data1 = new BigDecimal(data1s);
                BigDecimal data2 = new BigDecimal(data2s);
                if (ascFlag) {
                    //升序
                    return data1.compareTo(data2);
                } else {
                    //降序
                    return data2.compareTo(data1);
                }

            }
        });
    }

    public static Field[] getAllFields(Class<?> clazz){
        List<Field> fieldList = new ArrayList<>();
        while (clazz != null && !clazz.getName().toLowerCase().equals("java.lang.object")){
            fieldList.addAll(new ArrayList<>(Arrays.asList(clazz.getDeclaredFields())));
            clazz = clazz.getSuperclass();
        }
        Field[] fields = new Field[fieldList.size()];
        return fieldList.toArray(fields);
    }
}

測試用例：

public static void main(String[] args) {
        List<Student> students = new ArrayList<>();
        Student studentA = new Student();
        studentA.setName("a");
        studentA.setAge("16");
        studentA.setScore("95");
        Student studentB = new Student();
        studentB.setName("b");
        studentB.setAge("16");
        studentB.setScore("83");
        Student studentC = new Student();
        studentC.setName("c");
        studentC.setAge("16");
        studentC.setScore("90");
        students.add(studentA);
        students.add(studentB);
        students.add(studentC);

        System.out.println("-----排序前----");
        for (Student student : students) {
            System.out.println("學(xué)生：" + student.getName() + "的分?jǐn)?shù)為[" + student.getScore() + "]");
        }
        System.out.println();

		//調(diào)用排序方法執(zhí)行降序
        SortUtil.sort(students, "score", false, Student.class);

        System.out.println("-----排序后----");
        for (Student student : students) {
            System.out.println("學(xué)生：" + student.getName() + "的分?jǐn)?shù)為[" + student.getScore() + "]");
        }

    }

測試結(jié)果如預(yù)期一致。

附：指定條件排序

實(shí)現(xiàn) List 排序有多種方法，本文總結(jié)以下幾種。

調(diào)用 list sort 方法，實(shí)現(xiàn)比較器接口進(jìn)行排序

package com.example.demo.help;

import java.util.*;

public class ListSortTest {
    public static void main(String[] args) {

        List<String> rules = new ArrayList<>();
        rules.add("30003");
        rules.add("20002");
        rules.add("10001");
        rules.add("40004");
        rules.add("60006");
        rules.add("50005");

        Map<String, Integer> ruleUpper = new HashMap<>();
        ruleUpper.put("10001", 1);
        ruleUpper.put("20002", 2);
        ruleUpper.put("30003", 3);
        ruleUpper.put("40004", 4);

        rules.sort(new Comparator<String>() {
            @Override
            public int compare(String o1, String o2) {
                return ruleUpper.getOrDefault(o1, Integer.MAX_VALUE) - ruleUpper.getOrDefault(o2, Integer.MAX_VALUE);
            }
        });
        System.out.println(rules);
        // [10001, 20002, 30003, 40004, 60006, 50005]
    }
}

調(diào)用 list sort 方法，通過 lambda 表達(dá)式實(shí)現(xiàn)排序

package com.example.demo.help;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ListSortTest {
    public static void main(String[] args) {

        List<String> rules = new ArrayList<>();
        rules.add("30003");
        rules.add("20002");
        rules.add("10001");
        rules.add("40004");
        rules.add("60006");
        rules.add("50005");

        Map<String, Integer> ruleUpper = new HashMap<>();
        ruleUpper.put("10001", 1);
        ruleUpper.put("20002", 2);
        ruleUpper.put("30003", 3);
        ruleUpper.put("40004", 4);

        rules.sort((o1, o2) -> (ruleUpper.getOrDefault(o1, Integer.MAX_VALUE) - ruleUpper.getOrDefault(o2, Integer.MAX_VALUE)));
        System.out.println(rules);
        // [10001, 20002, 30003, 40004, 60006, 50005]
    }
}

通過 Collections sort 方法，實(shí)現(xiàn)比較器接口進(jìn)行排序

package com.example.demo.help;

import java.util.*;

public class ListSortTest {
    public static void main(String[] args) {

        List<String> rules = new ArrayList<>();
        rules.add("30003");
        rules.add("20002");
        rules.add("10001");
        rules.add("40004");
        rules.add("60006");
        rules.add("50005");

        Map<String, Integer> ruleUpper = new HashMap<>();
        ruleUpper.put("10001", 1);
        ruleUpper.put("20002", 2);
        ruleUpper.put("30003", 3);
        ruleUpper.put("40004", 4);

        Collections.sort(rules, new Comparator<String>() {
            @Override
            public int compare(String o1, String o2) {
                return ruleUpper.getOrDefault(o1, Integer.MAX_VALUE) - ruleUpper.getOrDefault(o2, Integer.MAX_VALUE);
            }
        });
        System.out.println(rules);
        // [10001, 20002, 30003, 40004, 60006, 50005]
    }
}

總結(jié)

到此這篇關(guān)于Java如何根據(jù)實(shí)體指定字段值對其List進(jìn)行排序的文章就介紹到這了,更多相關(guān)Java實(shí)體指定字段值對List排序內(nèi)容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

您可能感興趣的文章: