Common Programming Errors When using if Statement in Programming with Java

1. Figure – Common programming errors
Case 1:
if (80 <= score <= 90)
System.out.println ("Grade = B");
if (80 <= score && score <= 90)
System.out.println ("Grade = B");
Case 2:
if (n1 = 0)
System.out.println ("Can not divide by zero");
if (n1 == 0)
System.out.println ("Can not divide by zero");
Case 3:
if (n1 < 0);
n1 = -n1;
if (n1 < 0)
n1 = -n1;

2. Case 4:
if (n1 >= 0)
System.out.println ("n1 is positive number");
else;
System.out.println ("n1 is negative number");
if (n1 >= 0)
System.out.println ("n1 is positive number");
else
System.out.println ("n1 is negative number");
Case 5:
if (n1 > n2)
temp = n1;
n1 = n2;
n2 = temp;
if (n1 > n2) {
temp = n1;
n1 = n2;
n2 = temp;
}