How TreeSet performs Automatic Sorting

Today, I learned a piece of code about the automatic sorting function through treeSet, and I 've been tossing for a long time.

There are always some doubts. The subsequent communication and debugging can explain the basic principles of Automatic Sorting:

Automatic Sorting can be achieved in two ways:

One type:

Package xyxysjxy. io; import java. io. bufferedReader; import java. io. bufferedWriter; import java. io. fileWriter; import java. io. IOException; import java. io. inputStreamReader; import java. util. comparator; import java. util. iterator; import java. util. set; import java. util. treeSet; public class StudentInfoImport {public static void main (String [] args) throws IOException {BufferedWriter bw = new BufferedWriter (new FileWriter ("f: \ student.txt"); Set
 
  
Ss = StudentTools. getStudent (); Iterator
  
   
Is = ss. iterator (); while (is. hasNext () {Student student = (Student) is. next (); bw. write (student. toString (); bw. newLine (); bw. flush ();} bw. close () ;}} class Student {private String name; private int cn; private int math; private int en; private int sum; public String getName () {return name ;} public void setName (String name) {this. name = name;} public int getCn () {return cn;} public void setCn (int cn) {this.cn = Cn;} public int getMath () {return math;} public void setMath (int math) {this. math = math;} public int getEn () {return en;} public void setEn (int en) {this. en = en;} public int getSum () {return sum;} public void setSum (int sum) {this. sum = sum;} public Student (String name, int... is) {this. name = name; this.cn = is [0]; this. math = is [1]; this. en = is [2]; this. sum = cn + math + en;} @ Overridepublic String toStr Ing () {return "[name =" + name + "\ tcn =" + cn + "\ tmath =" + math + "\ ten =" + en + "\ tsum =" + sum + "]";} @ Overridepublic boolean equals (Object obj) {if (! (Obj instanceof Student) throw new ClassCastException ("unforced conversion"); Student s = (Student) obj; return s. name. equals (this. name) & s. sum = s. sum ;}@ Overridepublic int hashCode () {return sum * 78 + name. hashCode () ;}} class StudentTools {static Comparator
   
    
Com = new Comparator
    
     
() {@ Overridepublic int compare (Student o1, Student o2) {int sum = new Integer (o1.getSum ()). compareTo (new Integer (o2.getSum (); if (sum = 0) return o1.getName (). compareTo (o2.getName (); return sum ;}}; public static Set
     
      
GetStudent () throws IOException {return getStudent (com);} public static Set
      
        GetStudent (Comparator
       
         Com) throws IOException {Set
        
          StudentSet = null; if (com = null) studentSet = new TreeSet
         
           (); ElsestudentSet = new TreeSet
          
            (Com); BufferedReader br = new BufferedReader (new InputStreamReader (System. in); String len = ""; while (len = br. readLine ())! = Null) {if (len. equals ("over") break; String [] studentInfo = len. split (","); Student s = new Student (studentInfo [0], new int [] {Integer. parseInt (studentInfo [1]), Integer. parseInt (studentInfo [2]), Integer. parseInt (studentInfo [3])}); // when you add data to a HashSet, it will find the added object to implement the Comparable interface, studentSet. add (s) ;}return studentSet ;}}
          
         
        
       
      
     
    
   
  
 

Two types:

Package xyxysjxy. io; import java. io. bufferedReader; import java. io. bufferedWriter; import java. io. fileWriter; import java. io. IOException; import java. io. inputStreamReader; import java. util. comparator; import java. util. iterator; import java. util. set; import java. util. treeSet; public class StudentInfoImport {public static void main (String [] args) throws IOException {BufferedWriter bw = new BufferedWriter (new FileWriter ("f: \ student.txt"); Set
 
  
Ss = StudentTools. getStudent (); Iterator
  
   
Is = ss. iterator (); while (is. hasNext () {Student student = (Student) is. next (); bw. write (student. toString (); bw. newLine (); bw. flush ();} bw. close () ;}} class Student implements Comparable
   
    
{Private String name; private int cn; private int math; private int en; private int sum; public Student (String name, int... is) {this. name = name; this.cn = is [0]; this. math = is [1]; this. en = is [2]; this. sum = cn + math + en;} @ Overridepublic String toString () {return "[name =" + name + "\ tcn =" + cn + "\ tmath =" + math + "\ ten =" + en + "\ tsum =" + sum + "]";} @ Overridepublic boolean equals (Object obj) {if (! (Obj instanceof Student) throw new ClassCastException ("unforced conversion"); Student s = (Student) obj; return s. name. equals (this. name) & s. sum = s. sum;} public int compareTo (Student o) {int sum = new Integer (this. sum ). compareTo (new Integer (o. sum); if (sum = 0) return this. name. compareTo (o. name); return sum ;}@ Overridepublic int hashCode () {return sum * 78 + name. hashCode () ;}} class StudentTools {public static Set
    
     
GetStudent () throws IOException {return getStudent (null);} public static Set
     
      
GetStudent (Comparator
      
        Com) throws IOException {Set
       
         StudentSet = null; if (com = null) studentSet = new TreeSet
        
          (); ElsestudentSet = new TreeSet
         
           (Com); BufferedReader br = new BufferedReader (new InputStreamReader (System. in); String len = ""; while (len = br. readLine ())! = Null) {if (len. equals ("over") break; String [] studentInfo = len. split (","); Student s = new Student (studentInfo [0], new int [] {Integer. parseInt (studentInfo [1]), Integer. parseInt (studentInfo [2]), Integer. parseInt (studentInfo [3])});
          
// When adding data to the HashSet, he will find the added object to implement the Comparable interface, studentSet. add (s) ;}return studentSet ;}}
          

          
Use the above two sections of code to explain the execution process:
          

          
Step 1: receive the value from the console and encapsulate it into a student object.
          
In fact, a TreeMap object is encapsulated in the treeSet.
          
When you call the ADD method, you actually call the put method.
          
 
While (len = br. readLine ())! = Null) {if (len. equals ("over") break; String [] studentInfo = len. split (","); Student s = new Student (studentInfo [0], new int [] {Integer. parseInt (studentInfo [1]), Integer. parseInt (studentInfo [2]), Integer. parseInt (studentInfo [3])});
// When adding data to a HashSet, he will find the added object to implement the Comparable interface, studentSet. add (s);} return studentSet; public TreeSet (Comparator
             Comparator) {this (new TreeMap <> (comparator ));}



Step 2: First, check.
This three-object Operator means this:
First, it judges whether you pass a comparator to the new treeset. 
Object. If it is passed, you can directly call the object you passed in.
But if you didn't pass in, then he will perform a type check,
The purpose of the check is to check whether you have implemented Comparable. If so, you can call your own method for implementing the interface.
Public V put (K key, V value) {Entry
              
               
T = root; if (t = null) {compare (key, key); // type (and possibly null) check (L type check) root = new Entry <> (key, value, null); size = 1; modCount ++; return null;} // when the object is stored for the first time, compared with itself, compare (key, key) final int compare (Object k1, Object k2) {return comparator = null? (Comparable
               ) K1). compareTo (K) k2): comparator. compare (K) k1, (K) k2 );}
              



Step 3: When you check whether you have implemented the compare interface or passed a compator object,
It will call your own implementation methods for comparison.
Return values:-, 1 to determine whether the values you are about to take and the size in the treeset are automatically sorted.