Java: How to properly remove a value from a HashMap NOT based on the key

Question

I have a Singleton class that inside has a HashMap. The HashMap is made of String and Set<String> :

private Map<String, Set<String>> mMap = new HashMap<>();

What I want to achieve?

Remove a given item from all the Set values inside the Map . For example:

mMap.put(keyName, new HashSet<String>())
....
mViewsSwipeStates.get(keyName).add("1");
mViewsSwipeStates.get(keyName).add("2");
mViewsSwipeStates.get(keyName).add("3");
....
//Remove an item from the set 
 mMap.values().remove("3"); //Does not work

What is the correct way to remove an item from inside the Set ?

Answer 1

I'm assuming you want to remove productCode from all the values of the Map (and not just from the value of a specific key).

You have to iterate over all the values of the Map , and remove from each of them the required element :

mMap.values().forEach(v->v.remove(productCode));

This code assumes there are no null values in the Map .

EDIT :

In Java 7 you can write:

for (Set<String> value : mMap.values()) {
    value.remove(productCode);
}

Answer 2

遍历所有映射条目，使每个映射条目的值发生变化：

map.forEach((k, v) -> v.remove(productCode)};

Answer 3

使用Java 8和Lambda表达式

map.forEach((key, value) -> value.remove(productCode));