CODEWITHSUNDEEP
javaarraysrandom
Austin Kregel
Austin Kregel

Reputation: 755

Adding random arrays to random arrays in java to make it equal another array

I am learning java, and from what I can tell, what I am looking to do is a rare situation.

I am trying to use an API (kindof) to randomly generate musical notes. I want it to generate 20 times so i have it in a for loop. I realize that i could have used a list for this I just dont know how I could have implemented it. The question I have is, when I try to compile this code, the first part runs. It lets me make the seed. However after that it gives me

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 2
at co.kbcomp.music.Main.main(Main.java:64)

What could I do to prevent this? I know that what I am doing is wrong. That much I dont need to be told. What I want to know is where am I going wrong.

package co.kbcomp.music;

import java.util.*;
import org.jfugue.*;
import java.util.Scanner; 

public class Main {

public static void main(String[] args){
    Scanner in = new Scanner(System.in);
    System.out.println("Please enter a number for the seed of the song");
    long seed = in.nextLong();

    Calendar cal = Calendar.getInstance();
    Random rand;
    //rand = new Random(cal.getTime());
    rand = new Random(seed);

    int NoteNumber = 0;
    int NoteLength = 0; 
    int OctiveNumber = 0;
    int ChordNumber = 0;
    int InversionNumber = 0;
    //int Duration = rand.nextInt(100 - 5) + 5;

    //This keeps track of the iteration of the for loop.
    String[] NN = { " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " "};
    String[] NL = { " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " "};
    String[] IN = { " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " "};
    String[] CN = { " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " "};
    String[] ON = { " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " ", " "};

    //This is what is being played
    String[] note = { "A", "B", "C", "D", "E", "F", "G" };
    String[] noteLength = {"", "w", "", "h", "", "q","", "i"};
    String[] octive = { "","1","",  "2", "", "3", "", "4", "", "5", "", "6", "", "7", "", "8", "", "9"};
    String[] chord = { "", "maj", "", "min"};
    String[] inversion = {"", "^", "", "^^", "", "^^^", "", "^^^^", "", "^^^^^"};
    String[] key = {"",""};
    String keys= " ";

    String randstr = " ";

    //this is the loop that defines the music legnth
    for (int i = 0; i < 21; i++) {

        NoteNumber = rand.nextInt(7);
        NoteLength = rand.nextInt(8);
        OctiveNumber = rand.nextInt(18);
        ChordNumber = rand.nextInt(4);
        InversionNumber = rand.nextInt(10);



        NN[i] = note[NoteNumber];           // This randomly generates the note to be played.
        NL[i] = noteLength[NoteLength];     // This randomly generates the length of the note.
        ON[i] = octive[OctiveNumber];       // This defines the octive to be played in.
        CN[i] = chord[ChordNumber];         // This is defines the major or the minor
        IN[i] = inversion[InversionNumber]; // IN[i] = inversion[InversionNumber];


        key[i] = NN[i] + NL[i] + ON[i] + CN[i] + IN[i];
        //randstr = c[0] + " " + c[1] + " " + c[2] + " " + c[3] + " " + c[4] + " " + c[5] + " " + c[6] + " " + c[7] + " " + c[8] + " " + c[9] + " " + c[10] + " " + c[11] + " " + c[12] + " " + c[13] + " " + c[14] + " " + c[15] + " " + c[16];
        keys = (key[0] + " " + key[1] + " " + key[2] + " " + key[3] + " " + key[4] + " " + key[5] + " " + key[6] + " " + key[7] + " " + key[8] + " " + key[9] +  " " + key[10] + " " + key[11] + " " + key[12] + " " + key[13] + " " + key[14] + " " + key[15] + " " + key[16] + " " + key[17] + " " + key[18] + " " + key[19] + " " + key[20]);
    }


    System.out.println(key);

    Player player = new Player();
    Pattern pattern = new Pattern(key[0]);
    player.play(pattern);



}
}

Upvotes: 0

Views: 127

Answers (3)

Francis
Francis

Reputation: 1090

You declare your key array with a length of two:

String[] key = {"",""};

But then later in your for loop, you try to access elements beyond the length of your array:

keys = (key[0] + " " + key[1] + " " + key[2] + " " + key[3] + " " + key[4] + 
       " " + key[5] + " " + key[6] + " " + key[7] + " " + key[8] + " " + key[9] + 
       " " + key[10] + " " + key[11] + " " + key[12] + " " + key[13] + " " +
       key[14] + " " + key[15] + " " + key[16] + " " + key[17] + " " + key[18] + 
       " " + key[19]  + " " + key[20]);

Since your array has only a length of two, when you try to access the third element (at array index 2), you get an ArrayIndexOutOfBoundsException.

Upvotes: 2

Scary Wombat
Scary Wombat

Reputation: 44854

As you array in only 20 in length

then this

for (int i = 0; i < 21; i++) {

is going to cause an overflow

It should be < 20

Plus this code is meaningless as your key is only an array of 2

keys = (key[0] + " " + key[1] + " " + key[2] + " " + key[3] + " " + key[4] + " " + key[5] + " " + key[6] + " " + key[7] + " " + key[8] + " " + key[9] +  " " + key[10] + " " + key[11] + " " + key[12] + " " + key[13] + " " + key[14] + " " + key[15] + " " + key[16] + " " + key[17] + " " + key[18] + " " + key[19] + " " + key[20]);

Upvotes: 0

atk
atk

Reputation: 9324

String[] key = {"",""};
...
for (int i = 0; i < 21; i++) {
    ...
    key[i] = ....

Do you see the problem?

Upvotes: 0

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