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https://docs.oracle.com/javase/tutorial/java/nutsandbolts/while.html

## while
如果敘述成立->執行, 直到條件不成立為止

while (boolean expression)
    // statement

Example:

int i = 0;
while (i < 5) {
    System.out.print(i + " ");
    i++;
}
// 0 1 2 3 4

迭代Array:

int[] arr = {0, 1, 2, 3, 4};
int i = 0;
while (i < 5) {
    System.out.println(arr[i]);
    i++;
}
// 0 1 2 3 4

## do while
執行->如果敘述成立->執行->.., 直到條件不成立為止

do {
    // statements
} while (boolean expression);

Example:

int i = 5;
do {
    System.out.print(i + " ");
    i--;
} while (i > 0);
// 5 4 3 2 1