Java class set-set

Set interface is Collection Interface Sub-interface, Set cannot insert repeating element in interface

Set frequently used subclasses of interfaces:

HashSet is a Set a subclass of the interface. Features: The inside can not store repeated elements, and the use of a hash of the storage mode. So there is no order.

Treeset is also Set a subclass of the interface. Features: The inside can not store repeated elements, and is ordered to store

TreeSet is stored in order. So it is necessary to set up a good collation,TreeSet Each object in the class must be implemented compatable interface talent enough normal use;

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) {//inference is not the same object

return true;

}

if (! ( Obj instanceofpersonal)) {//inference 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);

Use a class object of your own definition 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);

Implement HashSet function by defining class personal as an element

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