我正在制作一个模拟媒体播放器程序，允许用户输入，编辑，删除和查看所有曲目。非常基本，我知道。但是我想添加一个功能，允许每次选择“播放随机歌曲”时打印数组列表中的随机条目，以模拟音乐播放器的随机播放功能。 所以我的方法就像
public void playRandom()
{
System.out.println("Now Playing: " + *insert code here?* ")
}
我有3个数组列表，表示曲目名称，曲目年份和曲目艺术家，但是当我打印到屏幕时，我希望它以这样的方式显示它打印艺术家，然后是连字符，然后是曲目名称？< / p>
我的代码如下：
我的主要课程： 包ca1;
//imports the Random mechanism
import java.util.Random;
//imports the scanner
import java.util.Scanner;
public class MainClass extends UserInput {
public String nextInt;
public static void main(String[] args) {
//Links to the UserInput class to create an object that stores
//user input
UserInput ui = new UserInput();
//Creates new scanner object
Scanner input = new Scanner(System.in);
//Declares the int "opt" so it can be used in the menu
int opt;
//Calls Methods Class so methods can be used below
Methods methodsFunctions = new Methods();
//initial prompt only displayed when program is first ran
System.out.println("Welcome to your music library");
//Usig a do while loop so that the program keeps running until
//a specific condition is met, in this case it's when 0 is selected.
do
{
//Menu Prompts printed to the screen for the user to select from
System.out.println("........ \n");
System.out.println("Press 0 to Exit\n");
System.out.println("Press 1 to Add a Song\n");
System.out.println("Press 2 to View All Songs\n");
System.out.println("Press 3 to Remove a Song\n");
System.out.println("Press 4 to Edit Song Information\n");
System.out.println("Press 5 to Play Random Song\n");
System.out.println("Press 6 to Delete All Songs\n");
//Monitors the next Int the user types
opt = input.nextInt();
//"if" statements
if (opt == 0)
{
//This corresponds to the condition of the while loop,
//The program will exit and print "Goodbye!" for the user.
System.out.println("Goodbye!");
}
else if (opt == 1)
{
//This method allows the user to add a song to the library.
//With the format being Title, Artist, Year.
methodsFunctions.addEntry();
}
else if (opt == 2)
{
//This method prints the contents of the Array List to the screen
methodsFunctions.viewAll();
}
else if (opt == 3)
{
//This method allows the user to remove an indiviual song from
//their music library
methodsFunctions.removeOne();
}
else if (opt == 4)
{
//This method allows the user to edit the data of a particular
//and then prints the new value on screen
methodsFunctions.editItem();
}
else if (opt == 5)
{
//This method will print out "Now playing" followed by a random
//song to simulate a music player's shuffle effect.
//methodsFunctions.RandomSong();
System.out.println("Now Playing ");
}
else if (opt == 6)
{
//This method will clear all contents of the library.
//It will ask the user to confirm their choice.
methodsFunctions.clearAll();
}
else
{
//If the user selects an incorrect number, the console will
//tell the user to try again and the main menu will print again
System.out.println("Incorrect Entry, please try again");
}
} //do-while loop
while (opt > 0);
}
}
我的方法课程：
package ca1;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.Scanner;
public class Methods extends UserInput
{
Scanner input = new Scanner (System.in);
//Declare array lists
List<String> songName = new ArrayList<>();
List<String> songArtist = new ArrayList<>();
List<Integer> songYear = new ArrayList<>();
UserInput ui = new UserInput();
private Random newRandom;
public void clearAll(){
System.out.println("Are you sure?");
System.out.print("1: Yes \n2: No" + "\n");
System.out.print("");
int confirmDelete=input.nextInt();
if (confirmDelete == 1){
songName.clear();
songYear.clear();
System.out.println("Your music library has been cleared");
}
}
public void viewAll(){
System.out.println("\n");
for (int i = 0; i < songName.size(); i++){
int counter=i+1;
System.out.println(counter+": "+songArtist.get(i)+" - "+ songName.get(i)+ " (" +songYear.get(i)+") ");
}
System.out.println("\n");
}
public void addEntry(){
//System.out.print("Enter Name: ");
String newName = ui.getString("Enter the name of the track");
songName.add(newName);
String newArtist = ui.getString("Who performs this track");
songArtist.add(newArtist);
System.out.print("What year was the track released? ");
int newYear=input.nextInt();
songYear.add(newYear);
System.out.println("\n" + "Thank you, " +songName.get(songName.size()-1) + " has been added to the library.");
System.out.println("\n" + "Press 2 to view your library." + "\n");
/*
System.out.println("\n"+songName.get(songName.size()-1));
System.out.println("\n"+songArtist.get(songArtist.size()-1));
System.out.println("\n"+songYear.get(songYear.size()-1));
*/
}
public void removeOne(){
System.out.println(" Which song would you like to delete? (1 to "+songName.size()+")");
viewAll();
int remove=input.nextInt();
if (remove >songName.size()){
System.out.println("Invalid ");
}
else {
remove--;
System.out.println("Are you sure you would like to delete "+songArtist.get(remove)+" - "+songName.get(remove)+" (" +songYear.get(remove)+ ") from your music library?");
System.out.print("1: Yes \n2: No" + "\n");
int confirmDelete=input.nextInt();
if (confirmDelete == 1){
songArtist.remove(remove);
songName.remove(remove);
songYear.remove(remove);
System.out.println(songName.get(remove)+ " has just been removed from your music library");
// viewAll();
}
}
}
public void playRandom()
{
String RandomSong = (SongName.random);
System.out("Now playing + " RandomSong);
}
public void editItem(){
viewAll();
System.out.println("Choose the song you want to edit (1 to "+songName.size()+")");
//prints out the contents of library with first entry being index 1
//The library is numbered and goes as far as the index of the last entry
int edit=input.nextInt();
if (edit >songName.size()){
System.out.println("Invalid Selection");
//if user selects a number that corresponds to an index that's not
//In the array list, they will be shown an error.
}
else{
edit--;
System.out.println("\n" + "Enter New Track Name: ");
input.nextLine();
String editName=input.nextLine();
songName.set(edit,editName);
//Edits the songName value of the Song object selected
System.out.println("\n" + "Enter New Artist ");
String editArtist=input.nextLine();
songArtist.set(edit,editArtist);
//Edits the songArtist value of the Song object selected
System.out.println("\n" + "Enter New Year:");
int editYear;
editYear = input.nextInt();
songYear.set(edit,editYear);
//Edits the songName value of the Song object selected
System.out.print("\n" + "Your changes have been saved:" + "\n");
System.out.print("\n" + "This is your current library");
viewAll();
}
}
}
答案 0 :(得分：3)
我觉得你必须做那样的事情：
了解你的阵列有多长。例如，50首歌曲。然后，生成0到length-1之间的随机数。
public void playRandom()
{
int randomnumber =(int)(Math.random() * (length-1));
System.out.println("Now Playing: " + arrayOfSongName[randomnumber]);
}
然后你有一个随机曲目。