java 集合存储对象且根据对象属性排序

Posted 2020-12-04 A小小高

方法一：根据java1.8lambda表达式进行排序

Comparator<RateInfo> comparator = (t1, t2) -> t1.getRateCode().compareTo(t2.getRateCode());

方法二：使用List的方法sort()排序

List API:default void sort(Comparator<? super E> c)

其实也是依据Comarator这个类

rateInfolist.sort(comparator.reversed());

方法三：使用Collections类的sort进行排序

static <T> void sort(List<T> list, Comparator<? super T> c)

Sorts the specified list according to the order induced by the specified comparator.

谷歌翻译：根据指定比较器引发的顺序对指定列表进行排序。

其实该排序也是使用Comparator类进行排序

Comparator类API:英文翻译即可

int     compare(T o1, T o2)
Compares its two arguments for order.
static <T,U extends Comparable<? super U>>
Comparator<T>     comparing(Function<? super T,? extends U> keyExtractor)
Accepts a function that extracts a Comparable sort key from a type T, and returns a Comparator<T> that compares by that sort key.
static <T,U> Comparator<T>     comparing(Function<? super T,? extends U> keyExtractor, Comparator<? super U> keyComparator)
Accepts a function that extracts a sort key from a type T, and returns a Comparator<T> that compares by that sort key using the specified Comparator.
static <T> Comparator<T>     comparingDouble(ToDoubleFunction<? super T> keyExtractor)
Accepts a function that extracts a double sort key from a type T, and returns a Comparator<T> that compares by that sort key.
static <T> Comparator<T>     comparingInt(ToIntFunction<? super T> keyExtractor)
Accepts a function that extracts an int sort key from a type T, and returns a Comparator<T> that compares by that sort key.
static <T> Comparator<T>     comparingLong(ToLongFunction<? super T> keyExtractor)
Accepts a function that extracts a long sort key from a type T, and returns a Comparator<T> that compares by that sort key.
boolean     equals(Object obj)
Indicates whether some other object is "equal to" this comparator.
static <T extends Comparable<? super T>>
Comparator<T>     naturalOrder()
Returns a comparator that compares Comparable objects in natural order.
static <T> Comparator<T>     nullsFirst(Comparator<? super T> comparator)
Returns a null-friendly comparator that considers null to be less than non-null.
static <T> Comparator<T>     nullsLast(Comparator<? super T> comparator)
Returns a null-friendly comparator that considers null to be greater than non-null.
default Comparator<T>     reversed()
Returns a comparator that imposes the reverse ordering of this comparator.
static <T extends Comparable<? super T>>
Comparator<T>     reverseOrder()
Returns a comparator that imposes the reverse of the natural ordering.
default Comparator<T>     thenComparing(Comparator<? super T> other)
Returns a lexicographic-order comparator with another comparator.
default <U extends Comparable<? super U>>
Comparator<T>     thenComparing(Function<? super T,? extends U> keyExtractor)
Returns a lexicographic-order comparator with a function that extracts a Comparable sort key.
default <U> Comparator<T>     thenComparing(Function<? super T,? extends U> keyExtractor, Comparator<? super U> keyComparator)
Returns a lexicographic-order comparator with a function that extracts a key to be compared with the given Comparator.
default Comparator<T>     thenComparingDouble(ToDoubleFunction<? super T> keyExtractor)
Returns a lexicographic-order comparator with a function that extracts a double sort key.
default Comparator<T>     thenComparingInt(ToIntFunction<? super T> keyExtractor)
Returns a lexicographic-order comparator with a function that extracts a int sort key.
default Comparator<T>     thenComparingLong(ToLongFunction<? super T> keyExtractor)
Returns a lexicographic-order comparator with a function that extracts a long sort key.

代码：

Collections.sort(rateInfolist, Comparator.comparing(RateInfo::getRateCode));

方法四：使用Comparator的匿名对象类重写compare方法

代码：

Collections.sort(rateInfolist, new Comparator<RateInfo>(){
                    /*
                     * int compare(RateInfo R1, RateInfo R2) 返回一个基本类型的整型，
                     * 返回负数表示：R1 小于R2，
                     * 返回0 表示：R1和R2相等，
                     * 返回正数表示：R1大于R2
                     */
                    public int compare(RateInfo R1, RateInfo R2) {
                        Integer rateCode1 = Integer.parseInt(R1.getRateCode());
                        Integer rateCode2 = Integer.parseInt(R2.getRateCode());
                        //按照RateCode的年龄进行升序排列
                        if(rateCode1 > rateCode2){
                            return 1;
                        }
                        if(rateCode1 == rateCode2){
                            return 0;
                        }
                        return -1;
                    }
                });

自己写代码时遇到的问题，根据我的理解和网上的资料做的总结