Fill a list of arrays java

Question

I wanted to fill a list of arrays in Java I tried this in order to practice a little bit:

ArrayList <int []> temp = new ArrayList <int []>();
    for (int a = 1; a < 4 ; a++) {
        int [] array = new int [8];
            for (int i = 0; i < 8; i++) {
                array [i] = i*a;
            }
        System.out.println(array);
        temp.add(array);    
    }
System.out.println(temp);

This is the output I got

[[I@15db9742, [I@6d06d69c, [I@7852e922]

Please, why do i have this strange result ?

Answer 1

temp is defined as ArrayList <int []> , that is, a list of arrays. In Java, when you print something, eg. by calling System.out.println(temp) , the object in question is converted to a string by an implicit call to toString() . ArrayList overrides toString() and prints each of its elements in turn. For each element toString() is also called. However there is no toString() defined for int[] so you simply get the object reference, ie. the funny-looking string [I@6d06d69c . To print the value of temp in a meaningful fashion, you need to convert each int[] to something human-readable. The easiest way to do this is to make use of java.util.Arrays.toString() .

So you could try something like:

for (int[] element : temp) {
     System.out.println(Arrays.toString(element));
}

Answer 2

You are printing an ArrayList. Try using a loop to print or save your results.

For example:

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

You aren't supposed to directly print an arraylist.

Answer 3

When an array is printed its reference is shown, not its elements. Try replacing the array with another ArrayList .

Answer 4

What you are doing is that you are printing the Object class name representation then @ followed by Hashcode.

Your Output:

[I@15db9742, [I@6d06d69c, [I@7852e922]

I is the Object Class representation

Numbers followed by @ are Hashcode.

So, when you call this System.out.println(temp); , you are printing default representation of array . To get something meaningful and data from it you need to do like below:

System.out.println(java.util.Arrays.toString(temp));