Can Java HashMap key be repeated?
Keys in Java's HashMap cannot be repeated. If added repeatedly, HashMap will automatically overwrite the same data as the key, ensuring that one key corresponds to one value. When using it, just add the data in a HashMap Just add it to another HashMap according to the key.
Code example
Map param = new HashMap();
param.put("a","123");
system.out.println(param.get("a")); //123
param.put("a","456");
system.out.println(param.get("a")); //456HashMap common methods
(1) Insert key-value pair data
public V put(K key, V value)
(2) Get key-value pair data based on key value
public V get(Object key)
(3) Get the number of key-value pairs in the Map
public int size()
(4) Determine whether the Map collection contains key-value pairs with the key key
public boolean containsKey(Object key)
(5) Determine whether the Map collection contains a key-value pair with value
boolean containsValue(Object value)
(6 ) Determine whether there are no key-value pairs in the Map collection
public boolean isEmpty()
(7) Clear all key-value pairs in the Map collection
public void clear( )
(8) Delete the key-value pairs in the Map according to the key value
public V remove(Object key)
Recommended tutorial: "JavaTutorial"
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