Java class set-set

Set interface is Collection Interface Sub-interface, Set duplicate elements cannot be inserted in an interface

Set Common subclasses of interfaces:

HashSet is a Set a subclass of the interface, features: it can not store duplicate elements, and the use of hash storage, so there is no order.

Treeset is also Set a subclass of an interface, characterized by the inability to store repeating elements and to store them in an orderly manner.

TreeSet is ordered, so you need to set up the collation, TreeSet the class in which each object resides must implement the compatable The interface can be used normally;

Packageleiji;

Publicclass Person implements comparable<person> {

private String name;

private int age;

Public person (String Name,int age) {

This.name=name;

This.age=age;

}

Public String ToString () {//Overwrite toString method

Return "Name:" +name+ "; Age:" +age;

}

public int CompareTo (person per) {//Overwrite CompareTo method

if (this.age>per.age) {

return 1;

}

else if (this.age<per.age) {

return-1;

}

else{

Return This.name.compareTo (Per.name);

}

}

}

Packageleiji;

Publicclass Personal {

private String name;

private int age;

Public Personal (String Name,int age) {

This.name=name;

This.age=age;

}

Public String ToString () {//Overwrite toString method

Return "Name:" +name+ "; Age:" +age;

}

public boolean equals (Object obj) {//Overwrite Equals method

if (this==obj) {//judgment is not the same object

return true;

}

if (! ( Obj instanceofpersonal)) {//Judging is not the same class

return false;

}

personalp= (Personal) obj; Make a downward transition

if (This.name.equals (p.name) && this.age==p.age) {//

return true;

}else{

return false;

}

}

public int hashcode () {//overwrite hashcode function

Returnthis.name.hashCode () *this.age; Specify encoding format

}

}

Packageleiji;

Importjava.util.Set;

Importjava.util.HashSet;

Importjava.util.TreeSet;

Publicclass Sett {

public static void Main (String args[]) {

Set<string> allset=new hashset<string> ();

Allset.add ("A");

Allset.add ("M");

Allset.add ("D");

Allset.add ("F");

Allset.add ("F");

System.out.println (Allset);

Set<string> sortset=new treeset<string> ();

Sortset.add ("F");

Sortset.add ("M");

Sortset.add ("A");

Sortset.add ("D");

System.out.println (Sortset);

Using a custom class object as an element

Set<person> alls=new treeset<person> ();

Alls.add (New person ("Zhang San", 30));

Alls.add (New person ("Zhang San", 32));

Alls.add (New person ("Zhang San", 30));

Alls.add (New person ("John Doe", 30));

System.out.println (alls);

Using the custom class personal as an element to implement the HashSet function

Set<personal> allse=new hashset<personal> ();

Allse.add (New Personal ("Zhang San", 30));

Allse.add (New Personal ("John Doe", 30));

Allse.add (New Personal ("Zhang San", 30));

Allse.add (New Personal ("Zhao Liu", 30));

Allse.add (New Personal ("Xu Zheng Does", 30));

System.out.println (Allse);

}

}

// a good Object class Best Overwrite Object Class of hashcode () equals () toString () Three methods

Java class set-set