CODEWITHSUNDEEP
javalistarraylist
Sumit Nandi
Sumit Nandi

Reputation: 13

JAVA Arraylist unexpected output

Expected output : Cell-1 Cell-2 Cell-3 Cell-4

But the output that I am getting is : Cell-3 Cell-4 Cell-3 Cell-4

Why is this happening?

import java.util.ArrayList;

public class Test {
public static void main(String... a) {
    String[][] var1 = new String[] []{{"Cell-1","Cell-2"},{"Cell-3","Cell-4"}};
    ArrayList<String> r = new ArrayList<String>();
    ArrayList<ArrayList<String>> var = new ArrayList<ArrayList<String>>();

    //Insering data into the ArrayList.
    for(String[] row : var1){
        r.clear();
        for(String data : row){
            r.add(data);
        }
        var.add(r);
    }

    //Print data to console.
    for(ArrayList<String> r1 : var){
        for(String cell : r1)
            System.out.print(cell+" ");
        System.out.println();
    }
}

} `

Upvotes: 1

Views: 145

Answers (1)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726479

This is not unexpected at all: you add the same object, namely ArrayList r, to the ArrayList var twice. First, you add it when it has Cell-1 Cell-2, then you clear it, and then you add it with Cell-3 Cell-4. The problem is, when you call r.clear(), the array list that you added to var gets cleared as well.

You need to create a new ArrayList instead of clearing the existing one to fix this problem: replace r.clear() with r = new ArrayList<String>(), and the problem will go away.

Upvotes: 3

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