While-loops, Continue, and Break

while(bool_expr) { 
    ...
}

while(false) { // careful - loop is never executed
    ...
}

while(true) { // infinite loop - use ctrl + c if it won't terminate
    ...
} 

while(a < b) { // executes for b-a iterations 
    ...
    a++;
}

Example

Below are 3 fragments of code that all do the same thing: they print the number of even numbers between a and b exclusively.  We assume a and b have already been declared and initialized.

int numEven = 0;
int i = a + 1;
while(i < b) {
    numEven = (i % 2 == 0) ?  numEven + 1 : numEven;
    i++;
}
System.out.printf("Number of even numbers: %d\n", numEven);

int numEven = 0;
int i = a + 1;

while(true) {
    if (i == b) {
        break;
    }
    numEven = (i % 2 == 0) ?  numEven + 1 : numEven;
    i++;
}
System.out.printf("Number of even numbers: %d\n", numEven);

int numEven = 0;
int i = a + 1;

while(i < b) {
    if (i % 2 == 1) {
        i++;
        continue;
    }

    i++;
    numEven++;
}
System.out.printf("Number of even numbers: %d\n", numEven);

© 2017 – 2019, Eric. All rights reserved.