List自定义对象的排序，根据对象的某一列进行排序

   在工作中，经常需要对List对象集合进行排序操作，下面总结下搞个通用排序对象，原理是使用JAVA的  

   Comparator    接口实现排序   不多说直接上“干货”

1、存在实体类：

    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    class Book {
        private Long id;//编号
        private String userName;//书本名称
        private double productPrice;//书本价格
        private String author;//作者
        private Integer weight;//权重
    }

2、SortList  排序实现通用类：

@Data
@AllArgsConstructor
@NoArgsConstructor
public class SortList<T> implements Comparator<T> {

    //需要比较的对象属性字段名称
    private String  propertyName;
    //是否是升序排序
    private boolean isAsc;

    /**
     * 需要的是：根据类中的字段对对象进行排序
     *
     * @return
     */

    @Override
    public int compare(T b1, T b2) {

        Class<?> clz = b1.getClass();
        Method method = getPropertyMethod(clz, propertyName);
        try {

            Object objectOne = method.invoke(b1);

            Object objectTwo = method.invoke(b2);

            if (objectOne == null || objectTwo == null) {
                return 0;
            }

            Comparable value1 = (Comparable) objectOne;

            Comparable value2 = (Comparable) objectTwo;

            if (isAsc) {
                return value1.compareTo(value2);
            } else {
                return value2.compareTo(value1);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return 0;
    }

    // 获取类名
    public static Method getPropertyMethod(Class clz, String propertyName) {
        Method method = null;
        try {
            method = clz.getMethod("get" + firstUpperCase(propertyName));
        } catch (Exception e) {
            System.out.println("获取类名发生错误！");
        }
        return method;
    }

    /**
     * 首字母大写方法
     * @param str
     * @return
     */
    public static String firstUpperCase(String str) {
        char[] ch = str.toCharArray();
        if (ch[0] >= 'a' && ch[0] <= 'z') {
            ch[0] = (char) (ch[0] - 32);
        }
        return new String(ch);
    }

}

3、实际使用测试如下：  主要这么来使用   

Collections.sort(bookList, new SortList<Book>("productPrice",true));

测试

@Test
    public void sortBook() {
        List<Book> bookList = getBookList();
        System.out.println("原先的顺序：");
        printf(bookList);

        System.out.println("根据价格排序：");
        Collections.sort(bookList, new SortList<Book>("productPrice",true));
        printf(bookList);

        System.out.println("根据Id排序：");
        Collections.sort(bookList, new SortList<Book>("id",false));
        printf(bookList);

        System.out.println("根据weight排序：");
        Collections.sort(bookList, new SortList<Book>("weight",true));
        printf(bookList);

        System.out.println("根据userName排序：");
        Collections.sort(bookList, new SortList<Book>("userName",true));
        printf(bookList);


    }

    public List<Book> getBookList() {
        List<Book> books = Lists.newArrayList();
        Book book1 = new Book(1L, "first", 10.00, "zhangsan", 19);
        Book book2 = new Book(2L, "wirst", 9.00, "zhangsan", 24);
        Book book3 = new Book(3L, "eirst", 8.00, "zhangsan", 29);
        Book book4 = new Book(4L, "girst", 7.00, "zhangsan", 13);
        Book book5 = new Book(5L, "tirst", 6.00, "zhangsan", 14);

        books.add(book1);
        books.add(book2);
        books.add(book3);
        books.add(book4);
        books.add(book5);

        return books;
    }

    /**
     * 打印函数
     *
     * @param lisbk
     */
    public void printf(List<Book> lisbk) {
        if (lisbk.isEmpty() || lisbk == null) {
            System.out.println("没有数据");
            return;
        }
        for (Book book : lisbk) {
            System.out.println("Id: " + book.getId() + "   userName: " + book.getUserName() + "   price: " + book.getProductPrice() + "  weight:" + book.getWeight());
        }
        System.out.println();
        return;
    }

执行结果如下：