How can a Java variable be different from itself?

by

One simple way is to use Float.NaN:

float x = Float.NaN;  // <--

if (x == x) {
    System.out.println("Ok");
} else {
    System.out.println("Not ok");
}

Not ok

You can do the same with Double.NaN.

From JLS ยง15.21.1. Numerical Equality Operators == and !=:

Floating-point equality testing is performed in accordance with the rules of the IEEE 754 standard:

  • If either operand is NaN, then the result of == is false but the result of != is true.

    Indeed, the test x!=x is true if and only if the value of x is NaN.

…

More Related Contents:

  1. Why can't we declare variables in if statement?
  2. If-else One line statement (with string and integer) [closed]
  3. java if else errors not working properly
  4. Repeat the “if” statement if it has to go to the “else” statement
  5. Conditional Statement on Java7
  6. Android: If statement being skipped even if condition is correct
  7. Why am I getting “Error: ‘else’ without ‘if'”? [duplicate]
  8. New to Java and having issues writing and example
  9. Why is my if statement an error?
  10. Semicolon at end of ‘if’ statement
  11. What is the relative performance difference of if/else versus switch statement in Java?
  12. How can I check if an app running on Android?
  13. Error: ‘else’ without ‘if’
  14. && (AND) and || (OR) in IF statements
  15. Best way to format multiple ‘or’ conditions in an if statement
  16. Compiler error when declaring a variable inside if condition and no curly braces
  17. Java Swing; Two classes, where to put if statements and new actionlisteners?
  18. How to avoid a lot of if else conditions
  19. What is better: multiple “if” statements or one “if” with multiple conditions?
  20. How to check if a string starts with one of several prefixes?
  21. How to use this boolean in an if statement?
  22. Java if vs. try/catch overhead
  23. Refactoring if/else logic
  24. Short IF – ELSE statement
  25. How is String in switch statement more efficient than corresponding if-else statement?
  26. Which “if” construct is faster – statement or ternary operator?
  27. Nested if-else behaviour without braces
  28. “Wrong” return type when using if vs. ternary opertator in Java
  29. If-else working, switch not [duplicate]
  30. How is if/while condition evaluated when we use assignments instead of comparison?

Leave a Comment