如果我有一个用Java实现Map接口的对象,并且我希望对其中包含的每一对进行迭代,那么最有效的方法是什么?
元素的顺序是否取决于我对接口的特定映射实现?
如果我有一个用Java实现Map接口的对象,并且我希望对其中包含的每一对进行迭代,那么最有效的方法是什么?
元素的顺序是否取决于我对接口的特定映射实现?
当前回答
public class abcd{
public static void main(String[] args)
{
Map<Integer, String> testMap = new HashMap<Integer, String>();
testMap.put(10, "a");
testMap.put(20, "b");
testMap.put(30, "c");
testMap.put(40, "d");
for (Integer key:testMap.keySet()) {
String value=testMap.get(key);
System.out.println(value);
}
}
}
OR
public class abcd {
public static void main(String[] args)
{
Map<Integer, String> testMap = new HashMap<Integer, String>();
testMap.put(10, "a");
testMap.put(20, "b");
testMap.put(30, "c");
testMap.put(40, "d");
for (Entry<Integer, String> entry : testMap.entrySet()) {
Integer key=entry.getKey();
String value=entry.getValue();
}
}
}
其他回答
每个地图
简单地使用Map::forEach,其中键和值都传递给BiConsumer怎么样?
map.forEach((k,v)->{
System.out.println(k+"->"+v);
});
从Java10开始,您可以使用局部变量推理(也称为“var”)来减少许多现有答案的臃肿。例如:
for (var entry : map.entrySet()) {
System.out.println(entry.getKey() + " : " + entry.getValue());
}
这些都是迭代HashMap的所有可能方法。
HashMap<Integer,String> map=new HashMap<Integer,String>();
map.put(1,"David"); //Adding elements in Map
map.put(2,"John");
map.put(4,"Samyuktha");
map.put(3,"jasmin");
System.out.println("Iterating Hashmap...");
//way 1 (java 8 Method)
map.forEach((key, value) -> {
System.out.println(key+" : "+ value);
});
//way 2 (java 7 Method)
for(Map.Entry me : map.entrySet()){
System.out.println(me.getKey()+" "+me.getValue());
}
//way 3 (Legacy way to iterate HashMap)
Iterator iterator = map.entrySet().iterator();//map.keySet().iterator()
while (iterator.hasNext())
{
Map.Entry me =(Map.Entry)iterator.next();
System.out.println(me.getKey()+" : "+ me.getValue());
}
}
//Functional Oprations
Map<String, String> mapString = new HashMap<>();
mapString.entrySet().stream().map((entry) -> {
String mapKey = entry.getKey();
return entry;
}).forEach((entry) -> {
String mapValue = entry.getValue();
});
//Intrator
Map<String, String> mapString = new HashMap<>();
for (Iterator<Map.Entry<String, String>> it = mapString.entrySet().iterator(); it.hasNext();) {
Map.Entry<String, String> entry = it.next();
String mapKey = entry.getKey();
String mapValue = entry.getValue();
}
//Simple for loop
Map<String, String> mapString = new HashMap<>();
for (Map.Entry<String, String> entry : mapString.entrySet()) {
String mapKey = entry.getKey();
String mapValue = entry.getValue();
}
使用Java 7
Map<String,String> sampleMap = new HashMap<>();
for (sampleMap.Entry<String,String> entry : sampleMap.entrySet()) {
String key = entry.getKey();
String value = entry.getValue();
/* your Code as per the Business Justification */
}
使用Java 8
Map<String,String> sampleMap = new HashMap<>();
sampleMap.forEach((k, v) -> System.out.println("Key is : " + k + " Value is : " + v));