ocpjp – Tarik Billa

java.util.Arrays.asList when used with removeIf throws UnsupportedOperationException

April 9, 2024 by Tarik

java.util.Arrays.asList() produces a list from which it is impossible to remove elements, so it throws on a removal attempt. You could wrap it with ArrayList: List<Integer> ints = new java.util.ArrayList<>(java.util.Arrays.asList(1,20,20)); Update Arrays.asList() returns return new ArrayList<>(a); where ArrayList is not java.util.ArrayList, but java.util.Arrays.ArrayList (internal class), which does not allow removal.

Why can not I add two bytes and get an int and I can add two final bytes get a byte?

December 5, 2023 by Tarik

From the JLS 5.2 Assignment Conversion In addition, if the expression is a constant expression (§15.28) of type byte, short, char, or int: – A narrowing primitive conversion may be used if the type of the variable is byte, short, or char, and the value of the constant expression is representable in the type of … Read more

Formatting using printf and format

September 25, 2023 by Tarik

for “%b” : If the argument arg is null, then the result is “false”. If arg is a boolean or Boolean, then the result is the string returned by String.valueOf(). Otherwise, the result is “true”. reference

a = (a++) * (a++) gives strange results in Java [closed]

May 29, 2023 by Tarik

After the first a++ a becomes 4. So you have 3 * 4 = 12. (a becomes 5 after the 2nd a++, but that is discarded, because the assignment a = overrides it)

Why does Double.NaN==Double.NaN return false?

November 14, 2022 by Tarik

NaN means “Not a Number”. Java Language Specification (JLS) Third Edition says: An operation that overflows produces a signed infinity, an operation that underflows produces a denormalized value or a signed zero, and an operation that has no mathematically definite result produces NaN. All numeric operations with NaN as an operand produce NaN as a … Read more