问在Java中访问2D地图(Maps of Maps)的最有效方法是什么？EN正如您可以理解的那样，访问这些并赋值是一个繁琐的过程：您可以创建一个新的不可变的类(使用properly implementedequals()andhashCode()methods!)来存储两个整数键，并将其用作更简单的映射的键，而不是使用映射的映射。
HashBiMap capitalCountryMap=HashBiMap.create();capitalCountryMap.put("Berlin","Germany");capitalCountryMap.put("Cape Town","South Africa");String capitalOfGermany=capitalCountryMap.inverse().get("Germany"); 和BidiMap一样,BiMap也不允许通过相同的值获取多个键。如果你这么做,会得到ava.lang.IllegalArgum...
public interfaceMap<K,V> An object that maps keys to values. A map cannot contain duplicate keys; each key can map to at most one value. This interface takes the place of theDictionaryclass, which was a totally abstract class rather than an interface. ...
The locking is at a much finer granularity at a hashmap bucket level. ConcurrentHashMap doesn’t throw a ConcurrentModificationException if one thread tries to modify it while another is iterating over it. ConcurrentHashMap uses multitude of locks HashTable 线程安全,但是对整个Map上锁,读和写都需...
public class App extends Application { private MapView mapView; public static void main(String[] args) { Application.launch(args); } @Override public void start(Stage stage) { // set the title and size of the stage and show it stage.setTitle("Display a map tutorial"); stage.setWidth(...
a Map containing the specified mappings Attributes RegisterAttribute JavaTypeParametersAttribute ObsoleteAttribute Remarks Returns an unmodifiable map containing three mappings. See Unmodifiable Maps for details. Added in 9. Java documentation for java.util.Map.of(K, V, K, V, K, V). Portions of ...
public static void main(String[] args) { Map<String, String> identityMaps = new IdentityHashMap<String, String>(); identityMaps.put(new String("aa"), "aa"); identityMaps.put(new String("aa"), "bb"); identityMaps.put(new String("aa"), "cc"); identityMaps.put(new String("aa")...
The creation of the offline map can be fine-tuned usingparameter overrides for feature layers, or by usinglocal basemapsto achieve more customised results. Tags download, offline, save, web map Sample Code GenerateOfflineMapSample.java Use dark colors for code blocksCopy ...
将Map转成Set集合(keySet()),通过Set的迭代器取出Set集合中的每一个元素(Iterator)就是Map集合中的所有的键,再通过get方法获取键对应的值。 import java.util.HashMap; import java.util.Iterator; import java.util.Map; import java.util.Set; public class Maps { public static void main(String[] args)...
Java Maps的9个常见问题 一般来说,Map是一种由键值对组成的数据结构,其中键(key)在Map中是不能重复的; 本篇文章总结了9个最常见的问题(关于Java Map及其实现类); 出于简单考虑,在代码例子中我将不使用泛型,因此,我将仅仅写上Map而不是写上Map<K, V>,且Map中的Key和Value都是可以比较的,意味着K和V都...