custom hashmap in java

the length expands, the hash rules change as well. Let's review the hash formula:index = hashcode (Key) (Length-1) When the original array length is 8 o'clock, the hash operation is done with the 111B (representing the binary 7), and the new array length is 16,hash and 1111B (representing the binary 15). hash results are obviously different . The Java code for rehash is as follows: /** * Transfers all entries from the current table to newtable.

Hashmap sorting 1. sort by key For map sorting in Java, there is a Sort map, such as treemap. For this map, you can only sort by key first, and then sort by put and remove, performance may be compromised. In this solution, hashmap is used for creation and addition. If you want to sort by key, you can pass this hashmap

its hash function, any object that is a key must implement the Hashcode and Equals methods. The hashcode and Equals methods inherit from the root class object, and if you use a custom class as a key, be very careful, as defined by the hash function, if two objects are the same, that is, Obj1.equals (OBJ2) =true, Their hashcode must be the same, but if two objects are different, their hashcode is not necessarily different, and if the hashcode of two d

In-depth analysis and comparison of HashMap in Java-Linux general technology-Linux programming and kernel information. The following is a detailed description. In the world of Java, the structure processing of classes and various types of data is the key to the logic and performance of the entire program. As I encountered a problem that the performance and logic

Map interfaceInheritance diagram:Map Common methods Add, delete operations Object put(Object key, Object value) Object remove(Object key) void putAll(Map m) void clear Ways to manipulate meta views Set keySet() Collection values() Set entrySet() Element query operation Object get(Object key) boolean containsKey(Object key) boolean containsValue(Object value) int size() boolean isEmpty() boolean equals(Object obj)

Java basics: parsing HashMap and HashSet I. HashMap HashMap stores the data structure referenced by the "Key-Value" Object Based on the hash table. The saved key must have two key functions: (1) equals (): determines whether the two keys are the same to ensure the uniqueness of the saved Key; (2) hashCode (): Calcula

? ——3. Ways to resolve hash conflicts Open addressing Method (linear detection re-hash, two-time detection and re-hash, pseudo-random detection and hashing) Re-hash method Chain Address method Create a public overflow zone The solution to HashMap in Java is to use the chain address approach.4. Re-hashing the rehash processWhen the hash table capacity exceeds the default capacity, t

, an improved hash formula moves out of the sign bit, and then computes the remainder with the modulo (or%) operator.(123 0x7FFFFFFF)% 20 = 3(456 0x7FFFFFFF)% 20 = 16This ensures that you get a positive index value. If you look at the Java 8 HashMap source code, its implementation uses the following methods:a). prevent undesirable discrete values (poorer hashes) by extracting only important lows.b). The i

Turn from:Java HashSet and HashMap source analysisGeneral IntroductionThe reason why HashSet and HashMap together is explained, because they have the same implementation in Java, the former is only to the latter to do a layer of packaging, that is to say HashSet inside there is a HashMap(adapter mode). Therefore, this

Comparison in the Java world, regardless of class or data, the structure of the process is the logic of the entire program and the key to performance. Because I contacted a question about the coexistence of performance and logic, I began to study this problem. Searched the forum of big and Small, also "Java Virtual machine Specification", "apress,.java.collections." (2001),. Bm.ocr.6.0.shareconnector ", and

HashMap in Java is a key-value pair (Key-value) that stores elements. HashMap requires a hash function that uses the hashcode () and Equals () methods to add and retrieve elements to the collection/collection. When the put () method is called, HashMap calculates the hash value of the key and stores the key-value pair o

rehash can not be collected immediately. Then why not in the HashMap larger than the expansion of a little bit, I do not have a very satisfactory answer to this question, I only know that the hash of the modulo operation using a bitwise operation, the bitwise operation needs to limit the length of the array must be 2 exponent. In addition, Java heap memory is used in the tcmalloc of the library, their allo

In the world of Java, the structure processing of classes and various types of data is the key to the logic and performance of the entire program. As I encountered a problem that the performance and logic coexist at the same time, I began to study this problem. I searched for forums, large and small, and also read the Java Virtual Machine specification, apress ,. java