Common Methods for java-15.2 Collection

Common Methods for java-15.2 Collection

This section describes common Collection methods.

The following uses ArrayList as an example.

Package com. ray. ch14; import java. util. ArrayList; import java. util. Iterator; public class Test {public static void main (String [] args) {ArrayList
 
  
RtnList = new ArrayList
  
   
(); RtnList. add (1); // add method ArrayList
   
    
TempList = new ArrayList
    
     
(); TempList. add (2); rtnList. addAll (tempList); // addAll method System. out. println (rtnList. contains (1); // The contains method System. out. println (rtnList. containsAll (tempList); // containsAll Method for (Iterator
     
      
Iterator = tempList. iterator (); iterator. hasNext ();) {// Iterator iterator Integer item = (Integer) Iterator. next (); System. out. println (item);} System. out. println (rtnList. size (); // The size method rtnList. retainAll (tempList); // retainAll method rtnList. add (1); // add method rtnList. remove (1); // remove Method rtnList. removeAll (tempList); // removeAll method }}
     
    
   
  
 

Output:

True
True
2
2

Common Collection operations

Method	Meaning
Boolean add (E e)	Add specified Element
Boolean addAll (Collection c)	Add all elements in the specified collection to the new collection.
Void clear ()	Remove all elements
Boolean contains (Object o)	Checks whether the specified element is included. If true is returned, false is returned.
Boolean containsAll (Collection c)	Checks whether all elements of a Collection are contained. If true is returned, false is returned.
Boolean equals (Object o)	Compare the specified object
Int hashCode ()	Returns the hash value.
Boolean isEmpty ()	Empty or not
Iterator Iterator ()	Iterator
Boolean remove (Object o)	Remove objects
Boolean removeAll (Collection c)	Removes all elements of a Collection.
Boolean retainAll (Collection c)	Only the intersection of two collections is retained.
Object [] toArray ()	Returns an array containing all elements in the collection.
T [] toArray (T [])	Returns an array containing all elements in the collection. returns the same runtime type as the runtime type of the specified array.

Summary: This section describes common Collection methods.

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