Java HashMapJava 集合框架HashMap 是一个散列表,它存储的内容是键值对(key-value)映射。 HashMap 实现了 Map 接口,根据键的 HashCode 值存储数据,具有很快的访问速度,最多允许一条记录的键为 null,不支持线程同步。HashMap 是无序的,即不会记录插入的顺序。
In this tutorial, we will learn about the Java HashMap class and its methods with the help of examples. TheHashMapclass of the Java collections framework provides the hash table implementation ofthe Map interface. Java集合框架的HashMap类提供Map接口的哈希表实现。 Create a HashMap In order to ...
There are many ways to compareHashMaps in Java. We can compare them using theequals()method. The default implementation compares each value. If we change the inner Map’s contents, the equality check fails. If the inner objects are all new instances every time in the case of user-defined...
Java HashMap Methods clear() clone() compute() computeIfAbsent() computeIfPresent() containsKey() containsValue() entrySet() forEach() get() getOrDefault() isEmpty() keySet() merge() put() putAll() putIfAbsent() remove() replace() replaceAll() size() values() Java...
java数据结构之HashMap 一、HashMap源码注释 View Code 二、HashMap源码分析 1、HashMap的存储结构? HashMap底层是用一个数组table来存储键值对的Node,table的每个下标称为一个桶,通过key计算出来的hash值和table的长度计算出来下标值,键值对就存储在table的该下标处的桶中如果计算得到的下标相同就会被存入到同一个...
This null case is split out into separate methods * for the sake of performance in the two most commonly used * operations (get and put), but incorporated with conditionals in * others. * 查找null键对应值get()的替换版本。Null键映射到索引0,为了在两个最常用的操作(get和put)中执行性能,将...
Returns aCollectionview of the values contained in this map. Methods inherited from class java.util.AbstractMap equals,hashCode,toString Methods inherited from class java.lang.Object finalize,getClass,notify,notifyAll,wait,wait,wait Methods inherited from interface java.util.Map ...
importjava.util.HashMap;// import the HashMap classHashMap<String,String>capitalCities=newHashMap<String,String>(); Add Items TheHashMapclass has many useful methods. For example, to add items to it, use theput()method: Example // Import the HashMap classimportjava.util.HashMap;publicclas...
Since Java 9, we have factory methods for HashMap initialization. Main.java import java.util.Map; import static java.util.Map.entry; void main() { Map colours = Map.of(1, "red", 2, "blue", 3, "brown"); System.out.println(colours); Map countries = Map.ofEntries( entry("de", ...
3.4. UsingMap.putAll() Instead of iterating through all of the entries, we can use theputAll()method, which shallow-copies all of the mappings in one step: HashMap<String, Employee> shallowCopy = new HashMap<>(); shallowCopy.putAll(originalMap); ...