java - 'While'循环没有执行？

Question

我在我的代码中有一条评论来解释我的最终结果是什么，但请不要在回答这个问题时回答我如何实现这个目标。

基本上，我有一个标记为“currentNum”的 int，它等于 1。我有一个 while 循环要执行，直到 currentNum 小于 400 万。但是，由于某种原因，循环没有执行。while 循环之外的所有内容都会执行，但 while 循环本身不会。

'HI' 在控制台上显示一次。'LOOP' 不会显示在控制台中。

代码：

 /*Each new term in the Fibonacci sequence is generated by adding the previous two terms. 
  * By starting with 1 and 2, the first 10 terms will be:
  * 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
  * By considering the terms in the Fibonacci sequence whose values do not exceed four million, 
  * find the sum of the even-valued terms.*/

public class Solution {

public static void main(String args[]) {

    int lastNum1 = 0;
    int lastNum2 = 0;
    int currentNumEven = 0;
    int currentNum = 1;
    int sumEven = 0;
    boolean last = true;

    System.out.println("HI");

    while(currentNum < 4000000);

    System.out.println("LOOP");

    currentNum = currentNum + (lastNum1 + lastNum2);

    if(last) {
        lastNum1 = currentNum;
        last = !last;
    } else {
        lastNum2 = currentNum;
        last = !last;
    }

    if(currentNum % 2 == 0) {
        currentNumEven = currentNum;
        sumEven += currentNum;
        System.out.println(currentNumEven);
        System.out.println(currentNum);
    }

    if(currentNum < 4000000) {
    currentNum++;

    } else {
        System.out.println("Sum of all even Fibonacci values: " + sumEven + "\n Last even number of sequence below 4,000,000" + currentNumEven);
      }

   }

}

Answer 1

错误在这一行：

 while(currentNum < 4000000);

最后一个;错位了！在while条件之后，您应该放置一个开头{，然后}在循环末尾放置另一个，用于关闭该块。像这样：

while (currentNum < 4000000) {
    // body
}

Answer 2

语法错误。正确的语法是：

do{
 //put your codes here
}
while(currentNum < 4000000);

或者

while(currentNum < 4000000){
//put your codes here
}

Answer 3

使用 a;声明语句的结束。尝试这个：

public class Solution {

public static void main(String args[]) {

    int lastNum1 = 0;
    int lastNum2 = 0;
    int currentNumEven = 0;
    int currentNum = 1;
    int sumEven = 0;
    boolean last = true;

    System.out.println("HI");

    while(currentNum < 4000000){

    System.out.println("LOOP");

    currentNum = currentNum + (lastNum1 + lastNum2);

    if(last) {
        lastNum1 = currentNum;
        last = !last;
    } else {
        lastNum2 = currentNum;
        last = !last;
    }

    if(currentNum % 2 == 0) {
        currentNumEven = currentNum;
        sumEven += currentNum;
        System.out.println(currentNumEven);
        System.out.println(currentNum);
    }

    if(currentNum < 4000000) {
    currentNum++;

    } else {
        System.out.println("Sum of all even Fibonacci values: " + sumEven + "\n Last even number of sequence below 4,000,000" + currentNumEven);
      }
     }
   }

}

Answer 4

我相信这条线是你的问题所在

while(currentNum < 4000000);

这会导致无限循环，因为“currentNum”永远不会增加。

while(currentNum < 4000000);

==

while(currentNum < 4000000){
}