how does this work? - Java code -

so i've got piece of code,

package test1; class student13 {     public static void main(string [] args)      {         student13 p = new student13();         p.start();     }      void start()      {         long [] a1 = {3,4,5};         long [] a2 = fix(a1);         system.out.print(a1[0] + a1[1] + a1[2] + " ");         system.out.println(a2[0] + a2[1] + a2[2]);     }      long [] fix(long [] a3)      {         a3[1] = 7;         return a3;     }  } 

can tell me why returns 15 15 , not 12 15? function fix applied long[] a2, how come final result 15 15?

you pass a1 array fix(), called a3 in fix() method, regardless still referencing a1. when update a3: a3[1]=7, update paramater value of fix() a1. updated a1!