Interface Collection (topmost of all single set of interfaces)

Collection commonly used functions

Collection of all single parent interface is set, thus defining a single common set of methods (and List Set) in Collection, these methods can be used to operate all separate collection. Methods as below:

• public boolean add (E e): the given object to the current collection.
• public void clear (): Empty the collection of all the elements.
• public boolean remove (E e): Delete the given object in the current collection.
• public boolean contains (E e): determining whether the current collection contains the given object.
• public boolean isEmpty (): this determines whether the set is empty.
• public int size (): returns the number of elements in a set.
• public Object [] toArray (): the set of elements stored in the array.

Code Example

Package demo01; 

Import of java.util.ArrayList;
 Import java.util.Collection; 

/ * 
    java.util.Collection interfaces 
        topmost set of all single interface, defined inside a single set of common to all methods 
        of any single set may be used collection method of interface 


    methods in common: 
      public Boolean the Add (E E): the given object to the current collection. 
      public void clear (): Empty the collection of all the elements. 
      public boolean remove (E e): Delete the given object in the current collection. 
      public boolean contains (E e): determining whether the current collection contains the given object. 
      public boolean isEmpty (): this determines whether the set is empty. 
      public int size (): returns the number of elements in a set. 
      public Object [] toArray (): the set of elements stored in the array. 
 * / 
Public  class Demo01Collection {
     public static  void main (String [] args) {
         // create a set of objects, use polymorphic
         // Collection <String> = new new Coll the ArrayList <> (); 
        Collection <String> = Coll new new the ArrayList <> (); 
        the System. Out.println (Coll); //   [] 

        / * 
            public Boolean the Add (E E): the given object to the current collection. 
            The return value is a boolean value, generally returns true, so you can not received 
         * / 
        boolean B1 = coll.add ( "John Doe" ); 
        System.out.println ( "B1:" + B1); // B1: to true 
        System.out.println (Coll); // [Zhang] 
        coll.add ( "John Doe" ); "John Doe" ); 
        coll.add ( "Zhao six" ); 
        coll.add ( "Tianqi" ); 
        System.out.println (Coll); // [John Doe, John Doe Zhao six, pseudo-ginseng] 

        / * 
            public Boolean remove (E E): delete the given object in the current collection. 
            The return value is a boolean value, the presence of elements in the set, removing elements, returns true 
                                collection element does not exist, the delete fails, returns to false 
         * / 
        boolean B2 = coll.remove ( "Zhao six" ); 
        System.out.println ( " B2: "+ B2); // B2: to true 

        Boolean B3 = coll.remove (" ZHAO Si " ); 
        System.out.println ( " B3: "+ B3);
        System.out.println (Coll);// [John Doe, John Doe, pseudo-ginseng] 

        / * 
            public Boolean the contains (E E): this is determined whether the collection contains the given object. 
            Returns true comprising 
            not include the return to false 
         * / 
        Boolean B4 = coll.contains ( "John Doe" ); 
        System.out.println ( "B4:" + B4); // B4: true 

        Boolean B5 = coll.contains ( "Zhao four " ); 
        System.out.println ( " B5: "+ B5); // B5: to false 

        // public Boolean isEmpty (): this determines whether the set is empty. Returns a null set true, not empty return to false 
        Boolean B6 = coll.isEmpty (); 
        System.out.println ( "B6:" + B6); //B6: to false 

        //public int size (): returns the number of elements in a set. 
        int size = coll.size (); 
        System.out.println ( "size:" + size); // size:. 4 

        // public Object [] toArray (): the set of elements stored in the array. 
        Object [] = ARR coll.toArray ();
         for ( int I = 0; I <arr.length; I ++ ) { 
            of System.out.print (ARR [I]); // Zhangsanlisi Doe TianQi [] 
        } 
        the System.out .println ( "" );
         // public void the Clear (): empty the collection of all the elements. But not delete a collection, there is also a collection of 
        coll.clear (); 
        System.out.println (Coll); // []
        System.out.println(coll.isEmpty());//true
    }
}