Argthtjtr

  static void eldontes() {

    System.out.println("--- Choosing ---");

    int sorozat = new int{1, -1, 3, 5};

    boolean exists = false;

    for (int i = 0; i < sorozat.length && !exists; i++) {

        int elem = sorozat[i];

        if (elem < 0) {

            exists = true;

        }

    }



    System.out.println("There's negative: " + exists);

First of all, what's !exists in the for loop doing? !exist should mean that the boolean value is now true, shouldn't it?. So increment i utnil sorozat.length AND exists = true ? What does it mean?

Then here's this example:

static void buborekRendezes() {

    System.out.println("--- Bubble order ---");

    int sorozat = new int{9, 4, 6, 2, 3, 0, 5, 7, 8, 1};

    for (int i = sorozat.length - 1; i > 0; i--) {

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

            if (sorozat[j] > sorozat[j + 1]) {

                int tmp = sorozat[j];

                sorozat[j] = sorozat[j + 1];

                sorozat[j + 1] = tmp;

            }

        }

    }

    System.out.println(Arrays.toString(sorozat));

}

Starting from int tmp = sorozat[j]; I really don't know what's happening. What does the last three lines do? Why is the tmp on the right side at the end of the code?

for (int i = 0; i < sorozat.length && !exists; i++) {

        int elem = sorozat[i];

        if (elem < 0) {

            exists = true;

        }

    }

The !exists is to make sure the loop breaks as soon as the first negative value is found..

As per your next code fragment

for (int i = sorozat.length - 1; i > 0; i--) {

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

            if (sorozat[j] > sorozat[j + 1]) {

                int tmp = sorozat[j];

                sorozat[j] = sorozat[j + 1];

                sorozat[j + 1] = tmp;

            }

        }

    }

This is a basic working code for Bubble sort in java..Read the algorithm first and then it would be easier to understand the code.

int tmp = sorozat[j];

sorozat[j] = sorozat[j + 1];

sorozat[j + 1] = tmp;

These three lines are to swap the values present at sorozat[j] and sorozat[j+1]

First of all, what's !exists in the for loop doing?

In fact !exists means that the boolean variable exists is false.

!exists   (is equivalent to)    exists == false

And it's used here in the condition block of the for loop, to exit the loop whenever the elem<0 is met, in other words whenever exists == true.

for (int i = 0; i < sorozat.length && !exists; i++) {

    int elem = sorozat[i];

    if (elem < 0) {

        exists = true;

    }

}

So increment i utnil sorozat.length AND exists = true ? What does it mean?

No it means increment while i<sorozat.length and exists == false, whenever exists is set to true we will quit the loop.

1. You increment i not until but while i is less than sorozat.length AND !exists. Term !exists is equivalent to (exists == false). So your loop stops when you either reach the end of sorozat, or you find what you are looking for, that is, an element less than zero.




2. Here the values are exchanged between sorozat[j] and sorozat[j + 1]. In order to do this, the sorozat[j] value is stored inside tmp variable to avoid it being overwritten, then sorozat[j + 1] is put into sorozat[j], and finally initial sorozat[j] value taken from tmp is written into sorozat[j + 1]. Without tmp variable you would lose sorozat[j] value.

int tmp = sorozat[j];

sorozat[j] = sorozat[j + 1];

sorozat[j + 1] = tmp;

This is the basic algorythm to exchange the values of two variables.
Basically, is exchanging the values sorozat[j] and sorozat[j+1] using a temporal variable in the process (tmp).
So, if sorozat[j]=4and sorozat[j+1]=2 after that 3 lines the result would be sorozat[j]=2and sorozat[j+1]=4