Java HashMap 像 ArrayList 一样放入增强的 for 循环
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Java HashMap put in an enhanced for loop just like an ArrayList
提问by SwordW
For example, I can loop an ArrayListlike this
例如，我可以ArrayList像这样循环
for (String temp : arraylist)
Can I loop a HashMap by using the similar method?
我可以使用类似的方法循环 HashMap 吗？
采纳答案by Eran
You can iterate over the keys, entries or values.
您可以迭代键、条目或值。
for (String key : map.keySet()) {
String value = map.get(key);
}
for (String value : map.values()) {
}
for (Map.Entry<String,String> entry : map.entrySet()) {
String key = entry.getKey();
String value = entry.getValue();
}
This is assuming your map has String keys and String values.
这是假设您的地图具有字符串键和字符串值。
回答by Christopher Rivera
you can do
你可以做
for (String key : hashmap.keySet()) {
String value = hashmap.get(key);
}
回答by Mureinik
You can't directly loop a Maplike that in Java.
你不能Map在 Java 中直接循环 a 。
You can, however, loop the keys:
但是，您可以循环键：
for (SomeKeyObject key : map.keySet())
The values:
价值：
for (SomeValueObject value : map.values())
Or even its entries:
甚至它的条目：
for (Map.Entry<SomeKeyObject, SomeValueObject> entry : map.entrySet())
回答by huseyin tugrul buyukisik
public class IterableHashMap<T,U> extends HashMap implements Iterable
{
@Override
public Iterator iterator() {
// TODO Auto-generated method stub
return this.keySet().iterator();
}
}
public static void main(String[] args) {
testA a=new testA();
IterableHashMap test=a.new IterableHashMap<Object,Object>();
for(Object o:test)
{
}
}
回答by Tim Hallyburton
You can do it by using an Iteratorhttp://docs.oracle.com/javase/7/docs/api/java/util/Iterator.html.
您可以使用Iterator http://docs.oracle.com/javase/7/docs/api/java/util/Iterator.html 来完成。
HashMap<String, String> yourHashMap = new HashMap<>();
Iterator<Map.Entry<String, String>> it = yourHashMap.entrySet().iterator();
while(it.hasNext()){
it.next();
System.out.println(yourHashMap.get(it));
}
At first sight it might be tempting to use a for-loop instead of an Iterator, but
you will need an Iterator if you want to modify the elements in your HashMap while iterating over them!
When using a for-loop you cannot remove elements from your map while
乍一看，使用 for 循环而不是 Iterator 可能很诱人，但是
如果您想在迭代它们时修改 HashMap 中的元素，则需要一个 Iterator！
使用 for 循环时，您无法从地图中删除元素，而
it.remove()
would work well in the above example.
在上面的例子中效果很好。
回答by Rahul Jangra
Use this
用这个
map.forEach((k, v) -> System.out.printf("%s %s%n", k, v));
