Java Collection Exercises--topics

2. It is known that there are 16 men's football teams attending the 2008 Beijing Olympic Games. Write a program that divides the 16 teams randomly into 4 groups. Adopt List collection and random number

2008 Beijing Olympic Games men's race countries:

Côte d ' Ivoire, Argentina, Australia, Serbia, Netherlands, Nigeria, Japan, USA, China, new West Orchid, Brazil, Belgium, Korea, Cameroon, Honduras, Italy

Importjava.util.ArrayList;Importjava.util.List;ImportJava.util.Random; Public classFenzu { Public Static voidMain (string[] args) {List<String> qiudui=NewArraylist<>(); Qiudui.add (Ivorian); Qiudui.add (Argentina); Qiudui.add (Australia); Qiudui.add (Serbia); Qiudui.add (Netherlands); Qiudui.add (Nigeria); Qiudui.add (Japan); Qiudui.add (United States); Qiudui.add (China); Qiudui.add (New Zealand); Qiudui.add (Brazil); Qiudui.add (Belgium); Qiudui.add (Korea); Qiudui.add (Cameroon); Qiudui.add (Honduras); Qiudui.add (Italy); Random a=NewRandom ();  for(inti=0;i<4;i++) {System.out.print ("First" + (i+1) + "group:");  for(intj=0;j<4;j++) {String str=Qiudui.get (A.nextint (Qiudui.size ())); System.out.print (str+" ");            Qiudui.remove (str);        } System.out.println (); }    }}

3, have the following Student object,

private String name;

private int age;

private int score;

Private String Classnum;

Among them, Classnum represents the student's class number, for example "Class05". have the following List

List List = new ArrayList ();

List.add (New Student ("Tom", "Max", "Class05"));

List.add (New Student ("Jerry", "a", "Class04"));

List.add (New Student ("Owen", "Class05"));

List.add (New Student ("Jim", 30,80, "Class05"));

List.add ("Steve", "Student", "Class06"));

List.add (New Student ("Kevin", "Max", "Class04"));

On the basis of this list, complete the following requirements:

1) Calculate the average age of all students

2) calculate the average score for each class

Importjava.util.ArrayList;Importjava.util.List; Public classStudent {PrivateString name; Private intAge ; Private intscore; PrivateString Classnum; Student (String name,intAgeintscore, String classnum) {         This. name=name;  This. age=Age ;  This. score=score;  This. classnum=Classnum; }     Public Static voidMain (string[] args) {List<Student> list=NewArraylist<>(); List.add (NewStudent ("Tom", 18,100, "Class05")); List.add (NewStudent ("Jerry", 22,70, "Class04")); List.add (NewStudent ("Owen", 25,90, "Class05")); List.add (NewStudent ("Steve", 30,80, "Class05")); List.add (NewStudent ("Kevin", 28,66, "Class06")); List.add (NewStudent ("Tom", 18,100, "Class05")); intSum=0; intSumscore=0;  for(Student stu:list) {sum+=Stu.age; Sumscore+=Stu.score; } System.out.println ("Average age is:" +sum/list.size ()); System.out.println ("The average score is:" +sumscore/list.size ()); }}

5. The(Map) Design account object is as follows:

Private long ID;

private double balance;

private String password;

Requires a perfect design so that the account object can automatically assign IDs. Given a list as follows:

List List = new ArrayList ();

List.add (New account (10.00, "1234"));

List.add (New Account (15.00, "5678"));

List.add (New account (0, "1010"));

Requires the contents of the list to be placed in a map, the map key is ID, the value is the corresponding account object. Finally, traverse the map to print the ID and balance of all account objects.

Importjava.util.ArrayList;Importjava.util.List;ImportJava.util.Random; Public classAccount1 {Private LongID; Private Doublebalance; PrivateString password; List<Long> idjihe=NewArraylist<>(); Account1 (Doublebalance,string Password) {         This. balance=balance;  This. password=password; Random a=NewRandom (); Booleans=true;  while(s) {ID=A.nextlong (); if(id>0){                 This. id=ID; S=false; }            }        }     Public LonggetId () {returnID; }     Public voidSetId (LongID) { This. id=ID; }     Public DoubleGetBalance () {returnbalance; }     Public voidSetbalance (Doublebalance) {         This. Balance =balance; }     PublicString GetPassword () {returnpassword; }     Public voidSetPassword (String password) { This. Password =password; }    }

Importjava.util.ArrayList;ImportJava.util.HashMap;Importjava.util.List;ImportJava.util.Map; Public classTestaccount { Public Static voidMain (string[] args) {List<Account1> list=NewArraylist<>(); List.add (NewAccount1 (10.00, "1234")); List.add (NewAccount1 (15.00, "5678")); List.add (NewAccount1 (0, "1010")); Map<Long,Account1> map=NewHashmap<>();  for(Account1 temp:list) {map.put (Temp.getid (), temp); }         for(Long id:map.keySet ()) {System.out.println ("Id=" +id+ "balance is:" +map.get (ID). GetBalance ()); }    }}

Java Collection Exercises--topics