Identify all the errors in the following repetitive statements.

while (z < 1 && z > 100)
{
    a = b;
}

Convert the following for loop statement into the corresponding while loop and do-while loop:

int	sum = 0;
for	(int i= 0; i <= 100; i++)
    sum = sum + i;

Identify all the errors in the following repetitive statements.

for	(int i = 5; i > 0; i++)
{
    System.out.println("Java");
}

What is an empty statement? Explain its usefulness.