Assigning values ​​to an array index

Question

Please view the code snippet below and let me know how 1 2 comes out.

int[] a = { 1, 2, 3, 4 }; int[] b = { 2, 3, 1, 0 }; System.out.println( a [ (a = b)[3] ] ); System.out.println(a[0]); 

Actual answer 1 2

thanks

Answer 1

I will try to explain:

a [ (a = b)[3] ] will be executed in the following order:

• a [...] - the array a will be read and the link will be saved for this
• (a = b) - the variable a set to the reference array b
• (a=b)[3] - the 4th element of the array b is read (due to step 2) the value 0
• a [ (a = b)[3] ] - now this is equal to a[0] (due to steps 1 and 3) value 1

a[0] now gives 2 , since a refers to the array b (because of step 2), and the first element in this array is 2 .

Answer 2

Seriously, what is the purpose of this? Why would you ever want to do something that makes the code so unreadable. What do you expect from the result?

Result System.out.println( a [ (a = b)[3] ] ); linked to the order in which things are put on the evaluation stack.

• link to
• change the link stored in character a stored in b
• evaluated b [3] => 0
• print index 0 of the array to which the link was clicked at 1.), that is, the original a

so it prints the element at 0 of the original array a

System.out.println(a[0]); then just b[0]

Answer 3

The first two lines initialize your arrays. First sysout assigns b then a then prints [3], i.e. yours and now has values ​​{2,3,1,0}. The second sysout prints a [0].