double d1=7.95,d2=15.90; The double variable d1 and d2 are given initial values.

boolean x=(2*d1==15.90 && d2/2==7.95);
The first part 2*d1==15.90 would be true and second part d2/2==7.95 will also be true so x would contain true.
boolean y=(2*d1==15.90 || d2/2==7.95); Here first part 2*d1==15.90 would be true and since there is a || operator the second part will not be checked as first part is already true. So y will also contain true.
boolean z=(x || y); Since x is true so y need not checked and z would be true.

System.out.println(z);
So this would print true only