collections

问题 Java 8 is providing alternative hashing for String keys to improve performance when a large number of key hash code collisions are encountered. Can anybody explain what is that and how it will work? 回答1: From this email of core-lib-devs@openjkd : A new interface Hashable32 is introduced. Hashable32 provides a method hash32() String implements Hashable32 and hash32() method HashMap et al recognize String and invoke hash32() rather than hashCode() The revisions of the code: Murmur3 : https:/

问题 I need a list of strings and a way to quickly determine if a string is contained within that list. To enhance lookup speed, I considered SortedList and Dictionary ; however, both work with KeyValuePair s when all I need is a single string . I know I could use a KeyValuePair and simply ignore the Value portion. But I do prefer to be efficient and am just wondering if there is a collection better suited to my requirements. 回答1: If you're on .NET 3.5 or higher, use HashSet<String>. Failing that,

问题 I am preparing myself for an interview and I came across the followign question. I tried but I could not find anything which can create a class containing thread safe collection without "lock". If know any solution then please help. Create a C# class derived from Object and implements the following methods: AddString – This method should add a given string to an internal collection ToString – Override this method and return a single, comma-delimited string containing all the strings in the

问题 I am preparing myself for an interview and I came across the followign question. I tried but I could not find anything which can create a class containing thread safe collection without "lock". If know any solution then please help. Create a C# class derived from Object and implements the following methods: AddString – This method should add a given string to an internal collection ToString – Override this method and return a single, comma-delimited string containing all the strings in the

问题 I am using Java 8 (build 1.8.0_25), Netbeans 8.0.2 and am incorporating some of the Java 8 features into an existing app. Sorting and .forEach is not working so I have created some test code to ensure I understand lambdas, etc. and to diagnose the problem. Below is a mix of new code as well as code to interact with the data from my system: public void test(Registration reg) { /* new code */ List<String> family = new ArrayList<>(); family.add("Mom"); family.add("Dad"); family.add("Brother");

问题 I am using Java 8 (build 1.8.0_25), Netbeans 8.0.2 and am incorporating some of the Java 8 features into an existing app. Sorting and .forEach is not working so I have created some test code to ensure I understand lambdas, etc. and to diagnose the problem. Below is a mix of new code as well as code to interact with the data from my system: public void test(Registration reg) { /* new code */ List<String> family = new ArrayList<>(); family.add("Mom"); family.add("Dad"); family.add("Brother");

问题 I am using Java 8 (build 1.8.0_25), Netbeans 8.0.2 and am incorporating some of the Java 8 features into an existing app. Sorting and .forEach is not working so I have created some test code to ensure I understand lambdas, etc. and to diagnose the problem. Below is a mix of new code as well as code to interact with the data from my system: public void test(Registration reg) { /* new code */ List<String> family = new ArrayList<>(); family.add("Mom"); family.add("Dad"); family.add("Brother");

问题 I am using Java 8 (build 1.8.0_25), Netbeans 8.0.2 and am incorporating some of the Java 8 features into an existing app. Sorting and .forEach is not working so I have created some test code to ensure I understand lambdas, etc. and to diagnose the problem. Below is a mix of new code as well as code to interact with the data from my system: public void test(Registration reg) { /* new code */ List<String> family = new ArrayList<>(); family.add("Mom"); family.add("Dad"); family.add("Brother");

问题 Can somebody explain to me why is the method Iterator<E> iterator(); defined in java.util.Collection ? Collection already extends java.lang.Iterable ; this method is redundant. Is this for convenience? 回答1: The Collection interface was introduced in Java 1.2 with the Collections API. The iterator method was present then. However, the Iterable interface wasn't introduced until Java 1.5. The reason that Collection explicitly defines iterator is because it predates Iterable . The idea of a

问题 I have a Map that uses a Set for the key type, like this: Map<Set<Thing>, Val> map; When I query map.containsKey(myBunchOfThings), it returns false, and I don't understand why. I can iterate through each key in the keyset and verify there is a key that (1) has the same hashCode, and (2) is equals() to myBunchOfThings. System.out.println(map.containsKey(myBunchOfThings)); // false. for (Set<Thing> k : map.keySet()) { if (k.hashCode() == myBunchOfThings.hashCode() && k.equals(myBunchOfThings) {