确定质数 Java
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Determining Prime Numbers Java
提问by CBH
I am writing a program that takes as input an integer, and outputs a message whether the integer entered is prime or not. The algorithm I am using is as follows... Require:n>0, Require:isPrime <- true, fori=2 to sqrt(n) do, ifn%i=0 thenisPrime <- false end ifand end forThen Print whether the number is Prime or not. Here is my code so far, the code is not working and I am not able to find the problem.
我正在编写一个程序，该程序将一个整数作为输入，并输出一条消息，无论输入的整数是否为素数。我使用的算法如下... Require:n>0, Require:isPrime <- true, fori=2 to sqrt(n) do, ifn%i=0 thenisPrime <- false end ifand end forThen 打印数字是否为质数。到目前为止，这是我的代码，代码不起作用，我无法找到问题。
public static void main(String[] args) {
Scanner kb = new Scanner(System.in);
int n;
System.out.println("Input a positive integer");
n = kb.nextInt();
while (n>0){
boolean isPrime = true;
for (int i =2; i <= n/2;i++){
if(n % i == 0){
isPrime = false;
break;
}
}
if (isPrime = true){
System.out.println("The integer, " + n + ", is a prime");
break;
}
else{
System.out.println("The integer, " + n + ", is not a prime");
break;
}
}
}
}
I would be grateful if someone could help, Thanks!
如果有人能帮忙，我将不胜感激，谢谢！
采纳答案by rgettman
Your problem lies with this line:
你的问题在于这一行：
if (isPrime = true){
You made an assignment, instead of comparing to true, so the statement is always true.
您进行了赋值，而不是与 进行比较true，因此语句始终为true。
Use ==to compare boolean values, or better yet, since isPrimeis already a boolean:
使用==比较布尔值，或更好，但因为isPrime已经是boolean：
if (isPrime){
回答by Celeritas
In the text you say the algorithm you intend to implement checks integers up to the square root of nbut your code is going all the way up to n/2(see the for loop).
在文本中，你说你打算实现的算法检查整数的平方根，n但你的代码一直在n/2（参见 for 循环）。
The reason your current code isn't working is because if (isPrime = true)is an assignment operation and should be comparison if (isPrime == true)note the two equal signs.
您当前的代码不起作用的原因是因为if (isPrime = true)是赋值操作，应该比较if (isPrime == true)注意两个等号。
