Using a "Random" method to print out random index of Array List?

[RarkMowe]

Hi guys. I'm making a mock-media player program that allows the user to input,edit,delete and view all tracks. Pretty basic, I know. But I want to add a feature that allows a random entry in the array list to be printed each time "Play Random Song" is selected to simulate the shuffle function of a music player.
So my method would be like



public void playRandom()

{
System.out.println("Now Playing: " + *insert code here?* ")
}



I would really appreciate if somebody could show me how to achieve this? Thanks in advance!
My code is below:
________________________

package 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);

    }
}

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();
        }
    }
     
     
}

[DarrylBurke]

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[RarkMowe]

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Apologies, I added the code tags there.

[SJF]

Take a look at Math.random() Java Platform SE 6 (Java 6 API)

Math.random() returns a double between 0.0 and 1.0. Get the result from a random() call and multiply it by your maximum index (ie array.length - 1) and typecast to int. (int)(maxIndex * Math.Random()) will give you 0-maxIndex. This is a psuedo-random number generator, not suitable for crypto, but should get the job done here.

[RarkMowe]

Take a look at Math.random() Java Platform SE 6 (Java 6 API)

Math.random() returns a double between 0.0 and 1.0. Get the result from a random() call and multiply it by your maximum index (ie array.length - 1) and typecast to int. (int)(maxIndex * Math.Random()) will give you 0-maxIndex. This is a psuedo-random number generator, not suitable for crypto, but should get the job done here.

Thank you! I'm still having a problem though. This is the method I've come up with

            public void playRandom()
        {
            int randomSong =(int)(Math.random() * (songName.length-1));
            System.out.println("/n" + "Now Playing: " + (randomSong));
        }

I have an error underneath the .length-1 part that I can't get rid of. It's telling me it cannot find the symbol.

[SJF]

Apologies, you're using an ArrayList.

You want songName.size(); and
songName.get(int);

so, put it together:

    int randomSong =(int)(Math.random() * (songName.size()-1));                     //Generate an index into songName ArrayList 
    System.out.println("/n" + "Now Playing: " + songName.get(randomSong));      //Get the name of the song at that index and print it out