Thread: Array and loops.

What is it supposed to output? Can you explain what the code is supposed to do to generate its output?

Perhaps you should post the current version of the program with an explanation of what it is supposed to do.

Ok, I'm going to try to run you through this as detailed as possible. Because Norm explained your problem back on like page 1.

for( byte aryOneAdder = 1; aryOneAdder <121;){
            //Now what I want to happen here is the for loop increments aryOneAdder
            //till it's equal too 121. And store all the numbers in the aryOne array
             aryOneAdder++;
             byte[] aryOne = new byte[aryOneAdder];
             System.out.println(aryOne[0]);
}

Ok, we'll walk through the first 10 iterations.
1. aryOneAdder = 2; aryOne.length = 2; aryOne[0] = 0;
2. aryOneAdder = 3; aryOne.length = 3; aryOne[0] = 0;
3. aryOneAdder = 4; aryOne.length = 4; aryOne[0] = 0;
4. aryOneAdder = 5; aryOne.length = 5; aryOne[0] = 0;
5. aryOneAdder = 6; aryOne.length = 6; aryOne[0] = 0;
6. aryOneAdder = 7; aryOne.length = 7; aryOne[0] = 0;
7. aryOneAdder = 8; aryOne.length = 8; aryOne[0] = 0;
8. aryOneAdder = 9; aryOne.length = 9; aryOne[0] = 0;
9. aryOneAdder = 10; aryOne.length = 10; aryOne[0] = 0;
10. aryOneAdder = 11; aryOne.length = 11; aryOne[0] = 0;

Problems:
1. Notice how aryOne.length is changing as we go through the array, this shoudnt happen. But why is it happening? Because you construct byte[] aryOne = new byte[aryOneAdder]; INSIDE the loop that is iterating it. Which means that every time the loop iterates, it recreates aryOne with default values of 0. Create the array OUTSIDE of the loop, and problem solved.

2. You never reference array indexes 0 or 1. This is because you start your referencing at 1, and before you reference anything you increase it by 1. However, you are printing out array index 0, which means that it will ALWAYS print 0.

Here is my suggested fix:

//Construct Array Outside of Loop
byte[] aryOne = new byte[120];
//Start the loop at 1 AND put your incremention inside the FOR parameters so it will increment at the end
for( byte aryOneAdder = 0; aryOneAdder <120;aryOneAdder++)
{
             //This will store each index with their index value. 
             aryOne[aryOneAdder] = aryOneAdder
//Print out the value from the position we just inserted into
             System.out.println(aryOne[aryOneAdder]);
}

The array is created out of the for loop. Here is the current version of the code.

import java.util.Arrays;
class BirthdaySurprise {
    public static void main(String[] args){
        // here are all the people
        byte TSE = 122;
        short LA = 184;
        short ZE = 195;
        short AB = 199;
        int DE = 234;
        int HA = 349;
        int AL = 361;
        //That's the last one. The numbers are the number of the day that
        //each person's birthday comes on. So if your birthday comes on Jan 1
        //your variable will be equal to 1, and if on Dec31 it will be equal to 365.
        byte aryOneAdder;
        byte[] aryOne = new byte[123];
        for(aryOneAdder = 0; aryOneAdder <122;){
                if (aryOneAdder <121){
            aryOneAdder++;
            }
            aryOne[aryOneAdder] = aryOne[1];
         }
                System.out.println(Arrays.toString(aryOne));
    }
}

Since yesterday I've been unable to get any output when I run it, it just shows the progress bar below the output pane in NetBeans and doesn't seem to move at all.

      for(aryOneAdder = 0; aryOneAdder < 122;){
                if (aryOneAdder <121){
                     aryOneAdder++;
                 }
                aryOne[aryOneAdder] = aryOne[1];
                System.out.println("aryOneAddr=" + aryOneAddr): // Show current value of aryOneAddr
         } // end for()
         System.out.println(Arrays.toString(aryOne));

Add: System.out.println("aryOneAddr=" + aryOneAddr):
where its shown above and run the code.
What happens (or doesn't happen) when aryOneAddr is equal to 121?

it just shows the progress bar

That means the program is in a loop.

Printed out aryOneAddr=121 over 121 times.

Is that what you would expect from the code?

I would think it would print out forever or until the buffer got full or you stopped the program.

What code in the loop will stop the loop from going forever?

That would be because of this statement:

if (aryOneAdder <121){
            aryOneAdder++;
            }

There are two ways you can construct this loop. The way you currently have it will not reference index 0 and will never exit the loop. Your conditional statement in your loop, aryOneAdder < 122 will always be true because your if statement above will never allow the value to be larger than 121. So you are getting an infinite loop.

You seem to be constructing your for loop similar to how a while loop is constructed. To each their own, but I prefer to put the incrementation inside the FOR parameters.

If you want to reference index 0, here are the two ways of constructing this loop:

for(aryOneAdder = 0; aryOneAdder < 122;aryOneAdder++)
{
//Loop Code
}

In this one, notice how our statement, aryOneAdder++ is inside the FOR parameters. This is perfectly legal and the intended design of the FOR loop. The statement aryOneAdder++ will be executed every time the program reaches the end of the loop.

The second way of creating the loop would be more of a WHILE loop way, but it is more of how you are attempting it:

for(aryOneAdder = 0; aryOneAdder < 122;)
{
//Loop Code
aryOneAdder++;
}

Notice how our aryOneAdder++; statement is at the end of the loop and will execute every time. This will allow you to access array index 0 and still go through the loop.

Both of these loops do the exact same thing, it is just a different way of coding it.

import java.util.Arrays;
class BirthdaySurprise {
    public static void main(String[] args){
        // here are all the people
        byte TSE = 122;
        short LA = 184;
        short ZE = 195;
        short AB = 199;
        int DE = 234;
        int HA = 349;
        int AL = 361;
        //That's the last one. The numbers are the number of the day that
        //each person's birthday comes on. So if your birthday comes on Jan 1
        //your variable will be equal to 1, and if on Dec31 it will be equal to 365.
        byte[] aryOne = new byte[122];
        for( byte aryOneAdder = 0; aryOneAdder <=121;aryOneAdder++)
              {
             //This will store each index with their index value.
             aryOne[aryOneAdder] = aryOneAdder;
            //Print out the value from the position we just inserted into             
            }
        System.out.println(Arrays.toString(aryOne));
    }
}

Output:
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121]

Thanks guys!!! You have been a great deal of help!!

I'm getting an error message for this loop.

short[] aryLa = new short[70];
        for( short aryLaAdder = 123; aryLaAdder <=184;aryLaAdder++){
            //This will store each index with their index value.
             aryLa[aryLaAdder] = aryLaAdder;
             //Print out the value from the position we just inserted into
            }
        System.out.println("aryLa = " + Arrays.toString(aryLa));

Error message:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 123
at BirthdaySurprise.main(BirthdaySurprise.java:25)
Java Result: 1
BUILD SUCCESSFUL (total time: 1 second

Line 25:

  aryLa[aryLaAdder] = aryLaAdder;

ArrayIndexOutOfBoundsException: 123

short[] aryLa = new short[70];

What is the maximum index value you can have for the array aryLa?
What is the value of the first index used in your code?

yes, that is the problem

The contents of the array can be any valid short value. The values of the indexes into the array can only be from 0 to 69.

Originally Posted by Norm

The values of the indexes into the array can only be from 0 to 69.

A bit confused there.

short[] aryLa = new short[70];
With this array definition, the values of the index can be from 0 to 69.
The element: aryLa[70] does NOT exist.

I was thinking, my code looks good so far. But it would be much much better if I could make each persons variable equal to their DOB. Is there anyway that would be possible?

make each persons variable equal to their DOB.

What does that mean?
Is there a variable for each person? What type is the variable? String or int or a new class you're going to create?

Is your problem solved now?

You would have to say

String AL = "27/12/93";

I actually just did something with dates today. Made a whole class to allow me to work with mm/dd/yy date format the way I wanted to.

Updated code.

import java.util.Arrays;
 
class BirthdaySurprise {
    public static void main(String[] args){
        // here are all the people
        byte TSE = 122;
        short LA = 184;
        short ZE = 195;
        short AB = 199;
        int DE = 234;
        int HA = 349;
        int AL = 361;
//That's the last one. The numbers are the number of the day that
//each person's birthday comes on. So if your birthday comes on Jan 1
//your variable will be equal to 1, and if on Dec31 it will be equal to 365.
 
        byte[] aryTse = new byte[122];
        for( byte aryTseAdder = 0; aryTseAdder <=121;aryTseAdder++){
            //This will store each index with their index value.
             aryTse[aryTseAdder] = aryTseAdder;
             //Print out the value from the position we just inserted into
            }
 
        short[] aryLa = {123,124,125,126,127,128,129,130,131,132,133,134,135,136,
        137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,
        155,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,
        173,174,175,176,177,178,179,180,181,182,183};
 
        short[] aryZe = {185,186,187,188,189,190,191,192,193,194};
 
        short[] aryAb = {196,197,198};
 
        int[] aryDe = {200,201,202,203,204,205,206,207,208,209,210,211,213,214,
              215,216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,
              232,233};
 
        int[] aryHa = {235,236,237,238,239,240,241,242,243,244,245,246,247,248,
              249,250,251,252,253,254,255,256,257,258,259,260,261,262,263,264,265,
              266,267,268,269,270,271,272,273,274,275,276,277,278,279,280,281,282,
              283,284,285,286,287,288,289,290,291,292,293,294,295,296,297,298,299,
              300,301,302,303304,305,306,307,308,309,310,311,312,313,314,315,316,
              317,318,319,320,321,322,323,324};
 
        int[] aryAl = {350,351,352,353,354,355,356,357,358,359,360};
 
        int Today = DE;
 
        switch (Today) {
            case 122 :
                System.out.println("Happy Birthday Tsehaye!!");
                break;
            case 184 :
                System.out.println("Happy Birthday Almaz!!");
                break;
            case 195 :
                System.out.println("Happy Birthday Zewdit!!");
                break;
            case 199 :
                System.out.println("Happy Birthday Abraham!!");
                break;
            case 234 :
                System.out.println("Happy Birthday Desta!!");
                break;
            case 349 :
                System.out.println("Happy Birthday Habtam!!");
                break;
            case 361 :
                System.out.println("Happy Birthday Alem(one extra ! mark for you :D )!!!");
                break;
            default:
                System.out.println("Ohsnap! oh no!!! No birthdays today!!! :O");
        }
 
    }
}