Question

// Create a constant sentinel of -1
// “Prime” the loop
// Add the conditional to the loop so it continues
// as long as num is not equal to the sentinel

Scanner keyboard = new Scanner(System.in);   //data will be entered thru keyboard
while (...) {
    //process data
    num = keyboard.nextInt();
}

我对此感到困惑。我会在身体内部和身体内插入什么并制作-1的哨兵？在while循环中放置的适当条件是什么？那么我如何回答＆＃34;将条件添加到循环中的问题，只要num不等于sentinel＆＃34;？

Answer 1

这对你有用吗？

int sentinel = -1;

while(num != sentinel)
{
   // process data
   num = keyboard.nextInt();
}

Answer 2

使用do..while

int num = -1;
do {
    // process data 
    num = keyboard.nextInt(); 
} while(num != -1);

Answer 3

我会用这样的东西

int num = 0;
while(num != - 1)
{
num = keyboard.nextInt();
// whatever you want to do with num might want to put code in an if like
if(num != -1)
{
//do code
}
//also you could get the number at then end so you can do processing without the if     statement above
}

Answer 4

为了避免在使用num之前检查while是否已在num条件中以及在循环内再次达到标记值，请使用带有无限循环的break。

Scanner keyboard = new Scanner(System.in);   //data will be entered thru keyboard
for (;;) {
    num = keyboard.nextInt();
    if (num == -1) {
        break;
    }
    // use num
}

如何在while循环中使用扫描仪时“填充”循环并创建一个标记？

4 个答案: