问题在代码的注释中，对此感到抱歉，我认为这很整洁，因为流程很重要，我想...
import java.util.Scanner;
public class ReadingUserInput {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Please, enter 10 numbers, for example, from 1 to 100!");
int number = 0;
int total = 0;
int counter = 0;
while (counter < 10) {
System.out.println("Enter number #" + (counter + 1));
boolean hasNextInt = scanner.hasNextInt(); // here we open the prompt for user to enter the value/s*
// internally, we are ready to check if the input is going to be int
// user types the value/s and clicks enter
// let's presume, he/she typed '3'
// internally, user's input is like that (if Windows**) - '3\n'
// because when user presses Enter - \n is added to what he/she typed
if (hasNextInt) { // the app checks, ant it's int, that is, it's OK (true)
number = scanner.nextInt(); //here the application grabs user's input
//but, internally, it grabs only '3', because 'nextInt()' grabs only ints
// and doesn't "care" about the new feed/line - \n - character
// so, '\n' is left in Scanner's buffer!
counter++;
total += number;
} else {
System.out.println("Invalid Input! Try again!");
}
//scanner.nextLine(); // let's presume, this commented line, on the left of this line of comment, is absent in our code
// the flow of our code goes to boolean hasNextInt = scanner.hasNextInt();
// and again internally, we are ready to check if the input is going to be int
// and again the user is prompted (by a blinking cursor) to type his/her input
// and at this moment user types either a numeric again or a non-numeric character (a letter/letters)
// let's presume he/she is typing '4'
// and again, internally, user's input is actually like that (if Windows**) - '4\n'
// but scanner.hasNextInt() says 'OK', for the int is there! and it doesn't care about '\n'
//
// Now, let's presume that user (this time or next time) types 'a'
// Do we actually have 'a\n' ???
// and this time scanner.hasNextInt() says 'Alarm' - 'false'
// thus the input doesn't go to number = scanner.nextInt();
// So, does it mean that 'a\n' (or 'a') remains in Scanner's buffer???
// and it (scanner.hasNextInt()) kicks us to 'else'
// and we have an endless loop:
//Invalid Input! Try again!
//Enter number #...
//Invalid Input! Try again!
//Enter number #...
//Invalid Input! Try again!
//Enter number #...
//Invalid Input! Try again!
//Enter number #...
//Invalid Input! Try again!
//Enter number #...
//Invalid Input! Try again!
//Enter number #...
//Invalid Input! Try again!
//Enter number #...
//Why?
// Is there still 'a' (or 'a\n') and scanner.hasNextInt() throws the flow to 'else' endlessly,
// because "The scanner does not advance past any input"* ???
//
// or: there's only '\n', and again its not int, and we result in endless loop ???
// And finally, is that a different case? https://www.youtube.com/watch?v=_xqzmDyLWvs
// And PS: Is there anything wrong in my description in the comments?
// So what do we 'consume' by scanner.nextLine(); ???
}
scanner.close();
System.out.println("Thank you, your total is " + total);
}
}
// *来自Oracle：（https://docs.oracle.com/javase/6/docs/api/java/util/Scanner.html#hasNextInt%28%29）
“具有NextInt
公共布尔hasNextInt（）
如果可以使用nextInt（）方法将此扫描器输入中的下一个标记解释为默认基数中的int值，则返回true。扫描仪不会前进超过任何输入。”
// ** https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019KZDSA2
最佳答案
而是创建另一个扫描程序对象，而忽略内部缓冲区中剩余的内容。
public class ReadingUserInput {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Please, enter 10 numbers, for example, from 1 to 100!");
int number = 0;
int total = 0;
int counter = 0;
while (counter < 10) {
System.out.println("Enter number #" + (counter + 1));
boolean hasNextInt = scanner.hasNextInt();
if (hasNextInt) {
number = scanner.nextInt();
counter++;
total += number;
} else {
System.out.println("Invalid Input! Try again!");
scanner = new Scanner(System.in);
}
}
scanner.close();
System.out.println("Thank you, your total is " + total);
}
}
关于java - 无休止的循环-while循环内的scanner.hasNextInt()，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/61742991/