int [] (integer array) and object class relation in Java

Question

I know Object class is the root class of all classes in Java, I wanted to know the relation between int[] and Object class.

Arrays.stream() can accept arg of int[], long[], double[] and Object[].

As I came across a code which gives int[] to a generic type (Stream<int[]>), This code works, we provide only class to Stream.

Also the output to this code was hex code rather than integers

        int arr[] = { 1, 2, 3, 4, 5 }; 

        // --------- Using Arrays.stream() --------- 

        // to convert int array into Stream 
        IntStream intStream = Arrays.stream(arr); 

        // Displaying elements in Stream 
        intStream.forEach(str -> System.out.print(str + " ")); // {1,2,3,4,5]

        // --------- Using Stream.of() --------- 

        // to convert int array into Stream 
        Stream<int[]> stream = Stream.of(arr); 

        // Displaying elements in Stream 
        stream.forEach(str -> System.out.print(str + " ")); // I@asdf

What's your question? What's the error you want to fix? what's the expected output? — Victor Polo De Gyves Montero
– Victor Polo De Gyves Montero, Commented Mar 8, 2021 at 6:07
answer to title can be found in JLS 10. Arrays. First sentence: "In the Java programming language, arrays are objects (§4.3.1), are dynamically created, and may be assigned to variables of type Object (§4.3.2). All methods of class Object may be invoked on an array." — user15244370
– user15244370, Commented Mar 8, 2021 at 6:52
just for fun System.out.println(arr.getClass()) or Object obj = arr; int[] casted = (int[]) obj; — user15244370
– user15244370, Commented Mar 8, 2021 at 11:30
syso(arr.getClass()) // "[I" Makes sense toString() is Classname@hexcode — Jon B
– Jon B, Commented Mar 8, 2021 at 11:38

Gautham M · Accepted Answer · 2021-03-08 06:18:17Z

3

In intStream.forEach(str -> System.out.print(str + " ")); each str would be of type int. But in stream.forEach(str -> System.out.print(str + " ")); each str is of type int[]. Hence the difference in output.

To print a primitive array you need to use Arrays.toString like :

stream.forEach(str -> System.out.print(Arrays.toString(str) + "\n"));

edited Mar 8, 2021 at 6:18

answered Mar 8, 2021 at 6:11

Gautham M

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1 Comment

Jon B Over a year ago

This answered cleared things as well stackoverflow.com/questions/21949570/… This cleared the concept

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