for Loops
A for loop is used to repeat a statement until a condition is met.

for (initialization; test; increment) {
statement;
}

while Loops
The while loop repeats a statement for as long as a particular condition remains true.
Here’s an example:
while (a<3) {
x = x * a++; // the body of the loop
}

do-while Loops
The do loop is just like a while loop with one major difference—the place in the loop
when the condition is tested.
A while loop tests the condition before looping, so if the condition is false the first
time it is tested, the body of the loop never executes.
A do loop executes the body of the loop at least once before testing the condition, so if
the condition is false the first time it is tested, the body of the loop already will have
executed once.
Example
int a=1;
do {
a *= 3;
System.out.print(a + “ “);
} while (a < 30);