I'm learning Java and just came up with this subtle fact about the language: if I declare two integer Arrays with the same elements and compare them using == the result is false. Why does this happen? Should not the comparison evaluate to true?
public class Why {
public static void main(String[] args) {
int[] a = {1, 2, 3};
int[] b = {1, 2, 3};
System.out.println(a == b);
}
}
Thanks in advance!
Use Arrays.equals(arr1, arr2) method.
The == operator just checks if two references point to the same object.
Test:
int[] a = {1, 2, 3};
int[] b = a;
System.out.println(a == b); // returns true as b and a refer to the same array
int[] a = {1, 2, 3};
int[] b = {1, 2, 3};
System.out.println(Arrays.equals(a, b)); //returns true as a and b are meaningfully equal
No. ==compares numerical (or boolean) values, or references, only.
http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.21
You're probably looking for the Arrays.equals (a,b) method
If you use == operator with Object you are comparing the references, not the values.
If you use == operator with primitive types (int, long, boolean...) you are checking if they have the same values.
int[] a = {1, 2, 3};
int[] b = {1, 2, 3};
System.out.println(a == b); //return false;
System.out.println(a[0] == b[0]); //return true;
String[] a1 = {"Cat", "Dog", "Mouse"};
String[] b2 = {"Cat", "Dog", "Mouse"};
System.out.println(a1 == b1); //return false;
System.out.println(a1[0] == b1[0]); //return false; Because String are Object
You can use the Arrays.equals(array1, array2) method.
==compares references, not values.==will still give the right result (well for python at least, c# has its own downfalls there).