predicate

问题 Say i have a db-table looking like this: CREATE TABLE myTable( id BIGINT, date TIMESTAMP, user_ids JSONB ); user_ids are a JSONB-ARRAY Let a record of this table look like this: { "id":13, "date":"2019-01-25 11:03:57", "user_ids":[25, 661, 88] }; I need to query all records where user_ids contain 25. In SQL i can achieve it with the following select-statement: SELECT * FROM myTable where user_ids::jsonb @> '[25]'::jsonb; Now i need to write a JPA-Predicate that renders "user_ids::jsonb @> '

来源： https://stackoverflow.com/questions/64325939/first-order-logic-creating-terms-for-arithmetic-expressions-using-prolog

来源： https://stackoverflow.com/questions/35306595/problems-understanding-lower-bounds-when-used-with-lambda-and-functional-interfa

问题 I want to do a string list filter function using an Iterable<String> and a predicate to select the strings to keep, the other ones must be removed from the list, but I'm not understating how I do the remove. static <T> Iterable<T> select(Iterable<T> it, Predicate<T> pred) { for (T s: it) { if (pred.test(s)==false) { // what to do here? } } return ...; } For this input: {"a","","b",""} I expect {"a","b"} 回答1: An Iterable represents the capability to provide an Iterator on request. So, to

问题 I want to do a string list filter function using an Iterable<String> and a predicate to select the strings to keep, the other ones must be removed from the list, but I'm not understating how I do the remove. static <T> Iterable<T> select(Iterable<T> it, Predicate<T> pred) { for (T s: it) { if (pred.test(s)==false) { // what to do here? } } return ...; } For this input: {"a","","b",""} I expect {"a","b"} 回答1: An Iterable represents the capability to provide an Iterator on request. So, to

问题 Why does the below code return Predicate<String> and not boolean ? My understanding is that the !s.isEmpty() check here is going against the Predicate boolean test(T t); The return type here is boolean . So in my lambda should my nonEmptyStringPredicate not be of type boolean ? Obviously, it's not, I'm just trying to understand why it's not. Predicate<String> nonEmptyStringPredicate = (String s) -> !s.isEmpty(); 回答1: A Predicate gets in this case a String as parameter and returns a boolean .

问题 Why does the below code return Predicate<String> and not boolean ? My understanding is that the !s.isEmpty() check here is going against the Predicate boolean test(T t); The return type here is boolean . So in my lambda should my nonEmptyStringPredicate not be of type boolean ? Obviously, it's not, I'm just trying to understand why it's not. Predicate<String> nonEmptyStringPredicate = (String s) -> !s.isEmpty(); 回答1: A Predicate gets in this case a String as parameter and returns a boolean .

问题 What's the most idiomatic way to test whether all items of a collection match a predicate? Any item? 回答1: There are built-in functions for this: List(1,2,3,4).forall(x => x < 5) res0: Boolean = true for any: List(1,2,3,4).exists(x => x > 3) res1: Boolean = true 来源： https://stackoverflow.com/questions/15932137/checking-that-all-items-in-a-collection-match-a-predicate-in-scala

问题 What's the most idiomatic way to test whether all items of a collection match a predicate? Any item? 回答1: There are built-in functions for this: List(1,2,3,4).forall(x => x < 5) res0: Boolean = true for any: List(1,2,3,4).exists(x => x > 3) res1: Boolean = true 来源： https://stackoverflow.com/questions/15932137/checking-that-all-items-in-a-collection-match-a-predicate-in-scala

问题 I'm using Spring Boot with Spring JPA and Specification Executor. I have my Specification/Predicate combo successfully searching the simple attributes within my class. However, I am having difficulties searching the objects within. Do they need a separate Specification? I have a class that has 2 Many To One mapping classes within and would like to search those fields from within the same class. Predicate Implementation public Specification<User> getSpecification(SpecificationField field,