[英]My while loop goes into infinite loop, what's wrong?
I tried to write the BiggerThanPrime program which allows the user to give an input p and the program can find the next closest prime(n) to it such that the value of (np) is minimum. 我尝试编写BiggerThanPrime程序,该程序允许用户提供输入p,并且该程序可以找到与其最接近的素数(n),从而使(np)的值最小。
Here is my code: 这是我的代码:
static boolean Prime (int n){
boolean NotPrime = true;
boolean result = true;
for (int i=2; i< n; i++){
NotPrime = (n % i != 0);
result = (result && NotPrime);
}
return result;
}
//Using Betrand's Postulate which states that there always exists at least one prime p s.t.a< p <2a
public static void main(String[] args) {
int p = Integer.parseInt(args[0]);
int k = p+1;
while( k > p && k< 2*p){
if( Prime(k) == true){
System.out.println("the next bigger prime than "+ p + " is "+ k);
} else{
k++;
}
}
}
But the while loop goes into infinite loop. 但是while循环进入了无限循环。
Thus the result is : 因此结果是:
the next bigger prime than 20 is 23
the next bigger prime than 20 is 23
.
.
.
(infinitely goes on) :(
What am I doing wrong? 我究竟做错了什么?
You need to break the loop once you get the bigger prime number and also you need to increment k in each iteration as below: 一旦获得更大的质数,就需要中断循环,并且还需要在每次迭代中增加k,如下所示:
while( k > p && k< 2*p){
if(Prime(k)){
System.out.println("the next bigger prime than "+ p + " is "+ k);
break;
}
k++;
}
And also please note as Prime(k) returns a boolean value, It's not necessary again to compare it to true. 并且还请注意,由于Prime(k)返回一个布尔值,因此无需再次将其与true进行比较。
Once you find the next prime, you should break from the loop: 一旦找到下一个素数,就应该摆脱循环:
while( k > p && k< 2*p){
if( Prime(k) == true){
System.out.println("the next bigger prime than "+ p + " is "+ k);
break;
} else{
k++;
}
}
because you are not incrementing k
at each iteration 因为您没有在每次迭代中增加
k
Try this : 尝试这个 :
while( k > p && k< 2*p){
if( Prime(k) == true){
System.out.println("the next bigger prime than "+ p + " is "+ k);
}
k++;
}
while( k > p && k< 2*p){
if( Prime(k) == true){
System.out.println("the next bigger prime than "+ p + " is "+ k);
} else{
k++;
}
}
once Prime(k) returns true, you are not changing the value of k, thus loop continues. 一旦Prime(k)返回true,就不会更改k的值,因此循环继续。
when
( Prime(k) == true)
it will never increment the value of k.当
( Prime(k) == true)
,它将永远不会增加k的值。 So it will go to infinite loop.因此它将进入无限循环。
you can change the lop in either of this ways 您可以通过以下两种方式之一来更改
way 1: 方法1:
while( k > p && k< 2*p){
if( Prime(k) == true){
System.out.println("the next bigger prime than "+ p + " is "+ k);
}
k++;
}
Way 2 : 方式二:
while( k > p && k< 2*p){
if( Prime(k) == true){
System.out.println("the next bigger prime than "+ p + " is "+ k);
Break;
} else{
k++;
}
}
import java.util.*;
public class index_page
{
public static void main(String[] args) {
Scanner keyB = new Scanner(System.in);
String code = keyB.next();
while (!code.equals("01") || code.equals("02") || code.equals("00") || code.equals("03") || code.equals("04") || code.equals("05")){//Checking for erros in code from user
System.out.println("Invalid code!! Try again");
code = keyB.next();
}
}
}
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