Add, delete, modify, query for Java collections

Sub-class

1  Public classKecheng2 {3 4      PublicString ID;//declaring variable ID for a course5      PublicString name;//declaring variable The name of the course6     7      PublicKecheng (String id,string name)8     {9          This. id=ID;Ten          This. name=name; One          A     } -}

Experimental class

1 ImportJava.lang.reflect.Array;2 Importjava.util.ArrayList;3 Importjava.util.Arrays;4 ImportJava.util.Iterator;5 Importjava.util.List;6 7  Public classDemo18 {9 Ten      PublicList KC;//declaring objects KC belongs to the list type One      A      PublicDemo1 () -     { -          This. kc=NewArrayList ();//equivalent to list kc=new ArrayList (); the     } -      Public Static voidMain (string[] args) -     { -Demo1 Demo1 =NewDemo1 (); +Demo1.add ();//Add -Demo1.show ();//Check +         //Demo1.delall ();//Delete ADemo1.set ();//Modify atSystem.out.println ("====== deleted, modified ======"); -         //demo1.zqshow ();//Check -Demo1.itshow ();//Check -     } -  -     //The addition of the collection: in      Public voidAdd () -     { toKecheng k1=NewKecheng ("1", "Calligraphy appreciation" ); +Kecheng k2=NewKecheng ("2", "Wilderness Survival") ); -Kecheng k3=NewKecheng ("3", "Anime appreciation" ); theKecheng[] K4={K1,K2};//create an array, equivalent to kecheng[] k4={new Kecheng ("1", "Calligraphy Appreciation"), New Kecheng ("2", "Wilderness Survival")} *Kc.add (K1);//Individual Additions $ Kc.add (K2);Panax NotoginsengKc.add (0, K3);//the individual prescribed position is added, and the original set is postponed.  -Kc.addall (Arrays.aslist (K4));//The addition of the array. Array, using the class arrays to directly adjust the static Aslist method inside, returns the list type.  theKc.addall (0, Arrays.aslist (K4));//array Specifies the location to add. The original set is postponed.  +     } A      the     //Lookup Collection Contents: For Loop +      Public voidShow () -     { $          for(inti = 0; I < kc.size (); i++) $         { -Kecheng k= (Kecheng) kc.get (i);//use Kc.get (subscript) To set the object of the class in the collection, strongly to the type of the class, -System.out.println (k.id+ "," +k.name ");//You use the object of the class to fetch the properties of the class.  the         } -     }Wuyi      the     //Lookup Collection Contents: Enhanced for Loop -      Public voidzqshow () Wu     { -          for(Object OBJ:KC) About         { $Kecheng k1= (Kecheng) obj;//use the enhanced for loop to iterate through the objects of the class in the collection, strongly to the class type, -System.out.println (k1.id+ "," +k1.name ");//You use the object of the class to fetch the properties of the class.  -         } -     } A      +     //Lookup Collection Contents: iterator provided by the collection the      -      Public voiditshow () $     { theIterator It=kc.iterator ();//must have this step! If written directly as Kc.iterator (). Hasnext (), the wireless loop prints the first one.  the          while(It.hasnext ())//use the above object it to tune the iterator method.  the         { theKecheng it1 = (Kecheng) it.next ();//use the above object it to get the iterator method. Iterates through the objects of the class in the collection, strongly to the type of the class.  -System.out.println (it1.id+ "," +it1.name ");//You use the object of the class to fetch the properties of the class.  in         } the     } the      About     //Modify Set the      Public voidset () the     { theKc.set (0,NewKecheng ("2", "Wilderness Survival"));//new to replace the object at the specified position.  +     } -      the     //Delete RemoveBayi      the      Public voiddel () the     { -Kecheng k2= (Kecheng) kc.get (6);//You can only delete objects that are picked from the collection example! Instead of a new Object!!!  -Kc.remove (K2);//The first occurrence of the object in the collection can only be deleted, regardless of the location of the object to which it was transferred.  the     } the      the     //Delete RemoveAll the      -      Public voidDelall () the     { theKecheng[] k2={(Kecheng) Kc.get (5), (Kecheng) Kc.get (6)};//You can only delete objects that are picked from the collection example! Instead of a new Object!!!  theKc.removeall (Arrays.aslist (K2));//all the objects in the collection will be deleted!!! 94     } the      the      the}

Add, delete, modify, query for Java collections