Map.containsKey(Object key)
Returns true if this map contains a mapping for the specified key试验一下这个方法
Returns true if this map contains a mapping for the specified key试验一下这个方法
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Interface MapcontainsKey
public boolean containsKey(Object key)
Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains at a mapping for a key k such that (key==null ? k==null : key.equals(k)). (There can be at most one such mapping.) Parameters:
key - key whose presence in this map is to be tested.
Returns:
true if this map contains a mapping for the specified key.
Throws:
ClassCastException - if the key is of an inappropriate type for this map (optional).
NullPointerException - if the key is null and this map does not not permit null keys (optional).
public boolean containsKey(Object key) Returns true if this map contains a mapping for the specified key.example:
HashMap map = new HashMap();
map.containsKey(key);
Interface MapcontainsKey
public boolean containsKey(Object key)
Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains at a mapping for a key k such that (key==null ? k==null : key.equals(k)). (There can be at most one such mapping.) Parameters:
key - key whose presence in this map is to be tested.
Returns:
true if this map contains a mapping for the specified key.
Throws:
ClassCastException - if the key is of an inappropriate type for this map (optional).
NullPointerException - if the key is null and this map does not not permit null keys (optional).