java hashmap

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

the HashMap key, and string is most commonly used because the string is immutable and final, and the Equals () and Hashcode () methods have been overridden. Other wrapper classes also have this feature. Immutability is necessary, because in order to compute hashcode (), the key value should be prevented from changing 2. Adhere to the rules of overriding equals () and Hashcode () methods when using custom objects as keys to ensure that different objec

Java-HashMap analysis, javahashmap (1) Hash Algorithm Hash algorithm, which maps the original data to a shorter, fixed-length binary value through the hash function. The hash algorithm has two basic features: repeatable and irreversible. The hash value calculated theoretically can be repeated, but this is basically not the case for good hash functions. Irreversible means that the hash value cannot be used t

OldValue=value; Value=NewValue; returnOldValue; } Public Final Booleanequals (Object o) {if(! (Oinstanceofmap.entry))return false; Map.entry e=(map.entry) o; Object K1=GetKey (); Object K2=E.getkey (); if(K1 = = K2 | | (K1! =NULLk1.equals (K2))) {Object V1=GetValue (); Object v2=E.getvalue (); if(v1 = = V2 | | (V1! =NULLv1.equals (v2))) return true; } return false; } Public Final inthashcode () {returnObjects.hashcode (GetKey ()) ^Objects.hashcode (GetValue ()); } Public Fina

created here.So how did the user set the capacity hashmap initialized? Use the new HashMap (int capacity) constructor:Finally, the constructor is called, and the load factor is the default value. There is no new array, but a critical value is computed. In the previous picture Resize () method, if the table has a size of 0 and Newthr is greater than 0, the array is created according to the size of newthr. T

First of all, Hashmap,hashmap is a class, and all classes in Java inherit from an object class. The Hashcode () method is defined in the object class, in other words, any class will have this hashcode () method.So the Key.hashcode () function calls the hash function with the key key value type and returns the int hash value.First look at the two methods defined i

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

The difference between HashMap, HashSet, and Hashtable is a common interview topic for Java programmers, which is only recorded in this blog and is thoroughly analyzed in the source code:Before the analysis, the difference is listed below1:hashset the bottom of the HashMap implementation, but there is no key-value, only the H