SUMMARY | Data structures in Java

String

• The string class is non-modifiable, creating strings that need to be modified using StringBuffer (thread synchronization, higher security) or StringBuilder (thread is unsynchronized and faster).
• You can connect a string with "+".
• Creates a formatted string with String.Format ().

ArrayList

• dynamic Array, which can dynamically increase or decrease the element.
• Common operations:
  • Create:arraylist<type> arraylist=new arraylist<> ();
  • adding elements: Add
  • get element: Get
  • Delete element: Remove
  • Get array size: size
  • determine if an element is included: Contains
  • set element: Set
  • empty array: Clear
  • to determine if it is empty: IsEmpty
• Traversal by: Indexing index is the most efficient

•  type temp;  for  (int  i=0;i<arraylist.size () i++) {Temp
   =arraylist.get (i);}  

• ArrayList ordering requires implementing the comparator interface for custom sorting

• comparator<string> comparator=New comparator<string>() {    @Override      public int  Compare (String O1, String O2) {        ifreturn 1;         if return -1;         return 0;}    };

Stack

• Expanded by vector.
• Common operation: Push,peak,pop,search,isempty

•  Public Static voidstacktest () {Stack<String> stack=NewStack<string>(); //pressing elements into the top of the stackSystem.out.println (Stack.push ("haha")); System.out.println (Stack.push ("Yes")); //The search result for the top element of the stack is 1 and then increments from the top of the stack to the bottom of the stackSystem.out.println (Stack.search ("haha")); //view top of stack elementsSystem.out.println (Stack.peek ()); //pops the top element of the stack and returns the top element of the stackSystem.out.println (Stack.pop ()); //determine if the stack is non-emptySystem.out.println (Stack.isempty ());}

Queue

• is an interface that LinkedList implements the queue interface
• Common operation: Offer,peek,poll,isempty

•  Public Static voidqueuetest () {//LinkedList implements the queue interface, so it is constructed with LinkedListQueue<string> queue=NewLinkedlist<string>(); //increments the element at the end of the queue and returns whether it adds successSystem.out.println (Queue.offer ("abc"))); System.out.println (Queue.offer ("Def")); //returns the first element of the queue, which returns null if it is empty; (Ps:element throws an exception when the queue is empty)System.out.println (Queue.peek ()); //POPs the first element of the team and returns the first element of the team, returning null if the queue is emptySystem.out.println (Queue.poll ()); //determine if the queue is emptySystem.out.println (Queue.isempty ());}

LinkedList

• Doubly linked list, non-synchronous
• Common operation: Addfirst,addlast,add,getfirst,getlast,get,removefirst,removelast,remove,isempty

   Public Static voidlinkedlisttest () {LinkedList<String> linkedlist=NewLinkedlist<string>(); //in the chain list head Plus, tail Plus, any position Canadian dollarLinkedlist.addfirst ("haha"); Linkedlist.addlast ("Yali"); Linkedlist.add (1, "good"); //Output Link ListSystem.out.println ("first element:" +Linkedlist.getfirst ()); System.out.println ("Last element:" +linkedlist.getlast ());  for(intI=0;i<linkedlist.size (); i++) System.out.println (Linkedlist.get (i)); //Delete any position, head, tail of the linked list elementLinkedlist.remove (1);    Linkedlist.removefirst ();    Linkedlist.removelast (); //determine if the linked list is emptySystem.out.println (Linkedlist.isempty ());}

HashMap

• Non-synchronous

•  Public Static voidhashmaptest () {HashMap<string, integer> hashmap=NewHashmap<string, integer>(); //adding elements to the hash tableHashmap.put ("TP", 123); Hashmap.put ("ZP", 567);    System.out.println (HASHMAP); //facilitates a hash table with iterators     for(Iterator<entry<string, Integer>> iterator=Hashmap.entryset (). iterator (); Iterator.hasnext ();) {Entry<string, integer> entry=Iterator.next ();        System.out.println (Entry.getkey ());    System.out.println (Entry.getvalue ()); }    //find if the key is in a hash tableSystem.out.println (Hashmap.containskey ("he"))); //find if the hash table has this valueSystem.out.println (Hashmap.containsvalue (567)); //Delete a key-value pair from a hash tableHashmap.remove ("TP"); System.out.println (HASHMAP);}

SUMMARY | Data structures in Java