Common operation of List collection in Java _java

Directory:

1.list to add, get, delete elements;

Whether an element is contained in the 2.list;

In 3.list, the element values are changed (replaced) according to the index;

The index of the (judging) element in 4.list;

5. Judging according to the position of element index;

6. Regenerate a new list (intercepting collection) using the index position in the list;

7. Compare all the elements in the two list;

8. Judge whether the list is empty;

9. Returns the Iterator collection object;

10. Convert the collection to a string;

11. Convert the collection to an array;

12. Set type conversion;

Note: The code in the content is related.

1.list to add, get, delete elements;

Add the method:. Add (e);

The Fetch method is:. Get (index);

The removal method is:. Remove (index);

Delete by index;. Remove (Object o);

Deleted according to element content;

List<string> person=new arraylist<> (); 
      Person.add ("Jackie");  The index is 0//.add (e) 
      Person.add ("Peter");  Index is 1 
      person.add ("Annie");  The index is 2 
      person.add ("Martin");  The index is 3 
      person.add ("Marry");  The index is 4 
       
      person.remove (3);  . Remove (Index) 
      person.remove ("Marry");   . Remove (Object o) 
       
      String per= ""; 
      Per=person.get (1); 
      System.out.println (per);  . Get (index) for 
       
      (int i = 0; i < person.size (); i++) { 
        System.out.println (Person.get (i));//.get (index) 
      

Whether an element is contained in the 2.list;

Method:. Contains (Object o); return True or False

List<string> fruits=new arraylist<> (); 
      Fruits.add ("Apple"); 
      Fruits.add ("banana"); 
      Fruits.add ("Peach"); 
      For loop traversal list for 
      (int i = 0; i < fruits.size (); i++) { 
        System.out.println (Fruits.get (i)); 
      } 
      String applestring= "Apple"; 
      True or False 
      System.out.println ("Fruits contains apple:" +fruits.contains (applestring)); 
       
      if (Fruits.contains (applestring)) { 
        System.out.println ("I Like eating apples"); 
      else { 
        System.out.println ("I'm not happy"); 
      }

In 3.list, the element values are changed (replaced) according to the index;

Note. Set (index, Element); and. Add (index, Element); the difference;

String a= "White Dragon Horse", b= "Sand Monk", c= "eight precepts", d= "Tang's Monk", e= "Wu empty"; 
      List<string> people=new arraylist<> (); 
      People.add (a); 
      People.add (b); 
      People.add (c); 
      People.set (0, D);  . Set (index, Element);   Place d Tang to index 0 in the list, replacing a white Dragon horse 
      people.add (1, e);  . Add (index, Element);   Put e Wukong in the list of the index of 1, the original location of the B-Sha Monk after moving a 
       
      //enhanced for loop traversal list for 
      (String str:people) { 
        System.out.println ( STR); 
      } 

The index of the (judging) element in 4.list;

Note: The difference between indexOf () and LastIndexOf ();

List<string> names=new arraylist<> (); 
      Names.add ("Liu Bei");  Index of 0 
      names.add ("Guan Yu");  The index is 1 
      names.add ("Zhang Fei");  The index is 2 
      names.add ("Liu Bei");  The index is 3 
      names.add ("Zhang Fei");  The index is 4 
      System.out.println (Names.indexof ("Liu Bei")); 
      System.out.println (Names.lastindexof ("Liu Bei")); 
      System.out.println (Names.indexof ("Zhang Fei")); 
      System.out.println (Names.lastindexof ("Zhang Fei")); 

5. Judging according to the position of element index;

if (Names.indexof ("Liu Bei") ==0) { 
  System.out.println ("Liu Bei is Here"); 
} else if (Names.lastindexof ("Liu Bei") ==3) { 
  System.out.println ("Liu Bei Is There"); 
} else { 
  System.out.println ("Where is Liu Bei?") "); 
} 

6. Regenerate a new list (intercepting collection) using the index position in the list;

Methods:. Sublist (Fromindex, Toindex);. Size (); The method gets the number of elements in the list and

List<string> phone=new arraylist<> (); 
      Phone.add ("Samsung");  Index is 0 
      phone.add ("Apple");  Index 1 
      phone.add ("Hammer");  Index of 2 
      phone.add ("Huawei");  Index of 3 
      phone.add ("millet");  The index is 4 
      //The original list for traversal for 
      (String pho:phone) { 
        System.out.println (pho); 
      } 
      Generate a new list 
      phone=phone.sublist (1, 4);//.sublist (Fromindex, Toindex)   /////To regenerate a list with an object indexed by 1-4, but no elements indexed to 4 , 4-1=3 for 
      (int i = 0; i < phone.size (); i++) {//Phone.size () The method gets the number of elements in the list and 
        System.out.println ("The new list contains The element is "+phone.get (i)); 
      } 

7. Compare all the elements in the two list;

The Equals method for two equal objects must be true, but two hashcode equal objects are not necessarily equal objects

1.<br>if (person.equals (fruits)) { 
  System.out.println ("All elements in the two list are the same"); 
} else { 
  System.out.println ("All elements in the two list are different"); 
} 
2.     
if (Person.hashcode () ==fruits.hashcode ()) { 
  System.out.println ("We are the same"); 
} else { 
  System.out.println ("We are not the same"); 
} 

8. Judge whether the list is empty;

Null returns TRUE, NOT NULL returns false

if (Person.isempty ()) { 
  System.out.println ("Empty"); 
} else { 
  System.out.println ("not Empty"); 
} 

9. Returns the Iterator collection object;

System.out.println ("Return iterator Collection object:" +person.iterator ()); 

1+0. Converts a collection to a string;

String listring= ""; 
Listring=person.tostring (); 
System.out.println ("Convert the collection to a string:" +listring); 

11. Convert the collection to an array;

System.out.println ("Convert the collection to an array:" +person.toarray ()); 

12. Set type conversion;

1. Default type 
list<object> listsstrings=new arraylist<> (); 
for (int i = 0; i < person.size (); i++) { 
  Listsstrings.add (Person.get (i)); 
} 
2. Designated type 
list<stringbuffer> lst=new arraylist<> (); 
for (string String:person) { 
Lst.add (StringBuffer (String)); 
} 

Complete code:

Package MyTest01; 
Import java.util.ArrayList; 
 
Import java.util.List; public class ListTest01 {public static void main (string[] args) {//list Add, get, delete element List<stri 
      Ng> person=new arraylist<> ();  Person.add ("Jackie");  The index is 0//.add (e) person.add ("Peter");  Index is 1 person.add ("Annie");  The index is 2 person.add ("Martin");  The index is 3 person.add ("Marry");  The index is 4 person.remove (3);   . Remove (Index) person.remove ("Marry"); 
      . Remove (Object o) String per= ""; 
      Per=person.get (1);  System.out.println (per); . Get (index) for (int i = 0; i < person.size (); i++) {System.out.println (Person.get (i)); The. Get (Index)}//list always contains an element list<string> fruits=new arraylist<> () 
      ; 
      Fruits.add ("Apple"); 
      Fruits.add ("banana"); 
      Fruits.add ("Peach"); For loop traversal list for (int i = 0; I < fruitS.size (); 
      i++) {System.out.println (Fruits.get (i)); 
      String applestring= "Apple"; 
       
      True or False System.out.println ("Fruits contains apple:" +fruits.contains (applestring)); 
      if (Fruits.contains (applestring)) {System.out.println ("I like to eat apples"); 
      }else {System.out.println ("I am not happy"); 
      //list element values in the index (replace) String a= "White Dragon Horse", b= "Sand Monk", c= "eight precepts", d= "Tang's Monk", e= "Wu empty"; 
      List<string> people=new arraylist<> (); 
      People.add (a); 
      People.add (b); 
      People.add (c);  People.set (0, D);  . Set (index, Element)//position D Tang to index 0 in list, replace a white Dragon horse People.add (1, e);   . Add (index, Element); Put e Wukong in the list of the index of 1, the original location of the B-Sha monk after moving A//enhanced for loop traversal list for (String str:people) {System.out.print 
      ln (str); 
      //list the index of the (judging) element in the list<string> names=new arraylist<> ();  Names.add ("Liu Bei");  Index of 0 names.add ("Guan Yu"); 
     Index is 1 Names.add ("Zhang Fei");  The index is 2 names.add ("Liu Bei");  The index is 3 names.add ("Zhang Fei"); 
      The index is 4 System.out.println (Names.indexof ("Liu Bei")); 
      System.out.println (Names.lastindexof ("Liu Bei")); 
      System.out.println (Names.indexof ("Zhang Fei")); 
       
      System.out.println (Names.lastindexof ("Zhang Fei")); 
      According to the element index position of the judge if (Names.indexof ("Liu Bei") ==0) {System.out.println ("Liu Bei is Here"); 
      }else if (Names.lastindexof ("Liu Bei") ==3) {System.out.println ("Liu Bei Is there"); }else {System.out.println ("Where is Liu Bei?") 
      "); 
      /////////Use the index position in list to regenerate a new list (intercept set) list<string> phone=new arraylist<> ();  Phone.add ("Samsung");  Index is 0 phone.add ("Apple");  Index 1 Phone.add ("Hammer");  Index of 2 Phone.add ("Huawei");  Index of 3 Phone.add ("millet"); 
      The index is 4//the original list for traversal for (String Pho:phone) {System.out.println (pho); ///Generate new list phone=phone.sublist (1, 4); . sublist (Fromindex, Toindex)//re-using index 1-4 objectsGenerates a list, but does not contain an element with an index of 4, 4-1=3 for (int i = 0; i < phone.size (); i++) {//Phone.size () This method gets the number of elements in the list and S 
      Ystem.out.println ("The new list contains elements that are" +phone.get (i)); The Equals method for all elements//two equal objects in the two list must be true, but two hashcode equal objects are not necessarily equal objects if (person.equals Frui 
      ts)) {System.out.println ("all elements of the two list are the same"); 
      }else {System.out.println ("all elements of the two list are different"); 
      } if (Person.hashcode () ==fruits.hashcode ()) {System.out.println ("We are the same"); 
      }else {System.out.println ("We are not the same"); ///Determine if list is empty//NULL returns TRUE, Non-empty returns False if (Person.isempty ()) {System.out.prin 
      TLN ("Empty"); 
      }else {System.out.println ("not Empty"); 
       
      //Returns the Iterator collection Object System.out.println ("Return iterator Collection object:" +person.iterator ()); 
      Converts the collection to string listring= ""; 
      Listring=person.tostring (); System.out.println ("Convert a collection to a string:" +listring); 
       
      Converts a collection to an array, the default type System.out.println ("Convert a collection to an array:" +person.toarray ()); 
      Converts the collection to the specified type (friendly processing)//1. Default Type list<object> listsstrings=new arraylist<> (); 
      for (int i = 0; i < person.size (); i++) {Listsstrings.add (Person.get (i)); 
      //2. Specifies the type list<stringbuffer> lst=new arraylist<> (); 
      for (string String:person) {Lst.add (StringBuffer (string)); 
  private static StringBuffer StringBuffer (String string) {return null; } 
 
 
  }

Above this Java in the list of common operation of the collection is a small set to share all the content, hope to give you a reference, but also hope that we support the cloud habitat community.