super T> other) { Objects.requireNonNull(other); return (Comparator<T> & Serializable) (c1, c2) -> { int res = compare(c1, c2); return (res != 0) ? res : other.compare(c1, c2); }; } default <U> Comparator<T> thenComparing( Function<? super T, ? extends U> keyExtractor, ...
Function<? super T, ? extends U> keyExtractor, Comparator<? super U> keyComparator)怎么理解Function<? super T, ? extends U>这个声明呢,网上查了半天都在讲生产者消费者的的准则,但好像和这个又对不上号,苦思冥想快2天了。。。求解PS:还有为啥我觉得java的泛型系统像是个半成品,好多莫名其妙的限制啊...
superU>> Comparator<T>comparing(Function<?superT,? extends U> keyExtractor)// 从T类型对象提取U类型的排序字段,并返回一个根据此排序字段Comparator<T>static<T,U> Comparator<T>comparing(Function<?superT,? extends U> keyExtractor, Comparator<?superU> keyComparator) Function 是一个函数接口,包含一种...
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 typeT, and returns aComparator<T>that compares by that sort key using the specifiedComparator. ...
static <T,U extends Comparable<? super U>> Comparator<T> comparing(Function<? super T,? extends U> keyExtractor)接受一个从类型T中提取实现了Comparable接口的排序键的函数，并返回根据这个排序键进行比较的Comparator对象。我们看以下代码。UseComparator.java import java.util.List;import java.util.ArrayList...
static后面的<T, U extends Comparable<? super U>>,这是泛型方法的泛型参数声明部分,意思是:方法中有一种没有任何限制的参数类型T,另一种参数是实现了Comparable<? super U>接口的类U。 comparing()方法接受一个参数:Function<? super T, ? extends U> keyExtractor,这是一个函数引用,所引用的函数需要传入...
如果流中的数据还需要再做一些处理再比较,可以通过Comarator.comparing中的第一个参数,Function<? super T, ? extends U> keyExtractor来处理。例如: Comparator.comparing(k -> k, (a, b) -> { int n = Math.min(a.size(), b.size());
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 <K extends Comparable<? super K>,V>Comparator<Map.Entry<K,V>> Map.Entry.comparingByKey() ...
public interface Comparator<T> { // 定义自己的Comparator int compare(T o1, T o2); ... // 使用comparing方法定义Comparator public static <T, U extends Comparable<? super U>> Comparator<T> comparing(Function<? super T, ? extends U> keyExtractor){ ...
public static Predicate distinctByKey(Function super T, ?> keyExtractor) { Set seen = ConcurrentHashMap.newKeySet(); return t -> seen.add(keyExtractor.apply(t)); } 1. 2. 3. 4. 5. 6. 7. 8. 9. 当然,如果是并行stream,则取出来的不一定是第一个,而是随机的。