0 
public static void main(String[] args) {
     int var = 128;
     Integer i = var;
     int j = var;
     LinkedList<Integer> ll = new LinkedList<>();
     ll.add(var);
     System.out.println(i==j);
     System.out.println(i==ll.peek()); 
 }

Output:
true
false

The values of variable var below number 128 though gives correct output as:

Output:
true
true

Please explain why comparison fails for peek() on values above 127?

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  • 1
    You're not comparing an int to an Integer. You're comparing an Integer to another Integer. So you should use equals rather than == Commented Apr 11, 2020 at 10:28
  • 1
    I think you should read this question and you will get partial answer. Commented Apr 11, 2020 at 10:42

3 Answers 3

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2

Do it as follows:

System.out.println(i.equals(ll.peek()));

Remember, == compares the references, not the content.

Check Why is 128==128 false but 127==127 is true when comparing Integer wrappers in Java? to understand why it returned true for a number less than 128.

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4 Comments

how come == works at all if it is comparing the references?
@JunisvaultCo - do you mean how i==j returns true? If yes, that is because of Autoboxing and Unboxing.
he stated that i==ll.peek() returns true for var<128. And indeed, I've tested it with 127 andi t does. Why? It is comparing references.
@JunisvaultCo have a look at this
1

This is because of the Integer constant pool. Java maintains Integer pool from -128 to 127

private static class IntegerCache {
        static final int low = -128;
        static final int high;  //set to 127
}

So for values between -128 to 127, same reference would be returned from cache but for other values new Integer object would be created.

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0

the operator == checks for reference equality. Because Integer i is a Class type, as well as the returned value of ll.peak(), you should use the equals() method to compare them.

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