Explanation java code

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Explanation java code

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#1 by (2 votes)

1

import java.io.*;
import java.util.*;

public class E11 extends Thread {
public void run() {
    ArrayList<Integer> primos = new ArrayList<Integer>();
    boolean primo = true;
    for (int i = 1; i <= 100; i++) {
        for (Integer numero: primos) {
            if (numero != 1 && i % numero == 0) {
                primo = false;
                break;
            }else {
                primo = true;
            }               
        }
        if (primo) {
            primos.add(i);
            System.out.print(i + " ");
        }
    }
}

public static void main(String[] args){
    Thread primo = new E11();
    primo.start();
}

}

Good with the following code that I put above you, that says of the first 100 whole numbers, those that are cousins but the for I do not quite understand it. Can someone explain to me that for ?

Thanks in advance

java bucle-for arraylist

asked by Caldeiro 05.12.2018 в 19:35

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1 answer

___ ___ erkimt Listview in Uneven c # ______ qstntxt ___

I am filling a listview from a select to the Oracle database. This is the code.

%pre%

What this result presents to me:

Now ... what I need is for it to look something like this: } }

It would be to group the orders with the same id.

The select to the database is a view that would be this:

%pre%

______ azszpr220169 ___

Assuming that your query is ordered as you want, that is, the records are correct, what you should do would be something like this:

%pre%

What we are doing here is comparing the order with the previous one. If the order is different, we put all the data we want in the list .. If not, we leave those columns blank, and only fill the others.

This way you will achieve what you need. Notice that if the orders are different, I change the current order. And I start the first one in 0.

This is commonly known as control cuts.

___ Get all the indices of the same element

score 2 · Accepted Answer

In java there are several ways to iterate. Both are known as for and foreach ; the latter is used for collections of objects (Arrays, lists and other data structures) .

In this case, the for (Integer numero: primos) is known as foreach in other programming languages. This can also be written as for(int i = 0; i < primos.size(); i++) . Both do exactly the same, the difference is that in the second, to obtain an object within the ArrayList<Integer> is done with the method get(i) , while in the first (foreach) and directly extract the object where you are iterating, it is saved in numero , and automatically when it passes to the next item, numbers will be the next item.

The foreach syntax in java, or the for for iterating collections of objects, is as follows:

for (Class x : a){codigo aqui...}

Where:

Class is the class to which the collection of objects in the list to iterate belongs, in your case Integer , since the list will save objects of this class.
x is the variable to which each item of the list will be assigned (This will be seen later in more detail as it works)
a is the name of the list or collection, which must be declared and instantiated.

A simple example, let's say we want to print 5 numbers in a list, and we have 5 elements in a ArrayList :

5 | 4 | 9 | 5 | 7

With the for normal: for(int i = 0; i < primos.size(); i++) , to print them, we said that to obtain an object with this method we must use the get(i) method that is a member of ArrayList<> , therefore it is as follows:
```
for(int i = 0; i < primos.size(); i++){

   System.out.println(primos.get(i));

}
```

In this way we make sure that for every change of the for counter, the next element of the list of primes is printed, and so on until the same list ends.

With the foreach: for (Integer numero: primos) , it is not necessary to do this, since with the foreach , or with this type of for, at the end of the iteration, numero takes the next object from the list, if not there is more then the for ends automatically. Using the previous example of printing and arranging numbers, it looks like this:
```
for (Integer numero: primos){

    System.out.println(numero);

}
```

With this simple code the same previous result is achieved.

Now, the use already depends on your needs, the foreach is used when the search is linear, that is, one by one, when you want to scroll the list through all the elements as ordered in the ArrayList < > . If you want to scroll through the list in an unordered manner, or for example, from the middle of the list to the end, the normal for, not the foreach, is used.

I hope it has served you.