CODEWITHSUNDEEP
javamysqlsql
Rafif Ramadhan
Rafif Ramadhan

Reputation: 19

Is there a way to make a list in a list from a table?

This is the code that I have tried:

ArrayList<ArrayList<String>> select = new ArrayList<ArrayList<String>>();
ArrayList<String> selectin = new ArrayList<String>();
ResultSet lihat = st.executeQuery("select * from usersss");
        while (lihat.next()){
            selectin.set(0, lihat.getString("user"));
            selectin.set(1, lihat.getString("password"));
            selectin.set(2, lihat.getString("email"));
            select.add(selectin);       
        }

for (int i = 0; i<select.size();i++) {
            System.out.println(select.get(i));
        }

This is the result:

[kursi, meja, [email protected]]
[kursi, meja, [email protected]]
[kursi, meja, [email protected]]
[kursi, meja, [email protected]]

This is the desired result (the actual table):

[paosp,skajs,[email protected]]
[fisd,mole,[email protected]]
[trem,olo,[email protected]]
[kursi,meja,[email protected]]

It seems like the selectin list updates itself inside the select list. Is there a way to make it not do this?

Upvotes: 1

Views: 64

Answers (3)

Animesh Sahu
Animesh Sahu

Reputation: 8106

You are actually replacing the values in same reference of selectin variable. And select variable only contains the single reference selectin multiple times.

Create a new ArrayList for every new element in select, like this:

ArrayList<ArrayList<String>> select = new ArrayList<ArrayList<String>>();
ResultSet lihat = st.executeQuery("select * from usersss");

while (lihat.next()){
    ArrayList<String> selectin = new ArrayList<String>();
    selectin.add(lihat.getString("user"));
    selectin.add(lihat.getString("password"));
    selectin.add(lihat.getString("email"));
    select.add(selectin);       
}

for (int i = 0; i<select.size();i++) {
    System.out.println(select.get(i));
}

This will create a new object of ArrayList and everytime while loop runs.

And you'll get your expected result.

Upvotes: 1

backdoor
backdoor

Reputation: 901

The set() method of java.util.ArrayList class is used to replace the element at the specified position in this list with the specified element.

boolean add(Object o): This method is used to append a specificd element to the end of a list.

you should replace the set() with add() in the loop.

while (lihat.next() ) {
        selectin = new ArrayList<>();
        selectin.add( lihat.getString("user") );
        selectin.add( lihat.getString("password") );
        selectin.add( lihat.getString("email") );
        select.add( selectin );       
    }

Upvotes: 1

Klaus
Klaus

Reputation: 1731

I think your while loop should be

    while (lihat.next() ) {
        selectin = new ArrayList<>();
        selectin.add( lihat.getString("user") );
        selectin.add( lihat.getString("password") );
        selectin.add( lihat.getString("email") );
        select.add( selectin );       
    }

Since it is pass by reference, second iteration updates the firstly added arraylist. That is why the output is same after all iterations.

Upvotes: 2

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