线程“main”中的异常 java.lang.IllegalArgumentException：n 必须为正
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/4072594/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Exception in thread "main" java.lang.IllegalArgumentException: n must be positive
提问by chief
Here is my error message:
这是我的错误信息：
Exception in thread "main" java.lang.IllegalArgumentException: n must be positive
at java.util.Random.nextInt(Random.java:265)
at Game.generateSecretNumber(Game.java:44)
at Game.start(Game.java:32)
at Game.main(Game.java:18
My Code is:
我的代码是：
import java.util.Random;
import java.util.Scanner;
public class Game {
private final int LOWER_BOUND = 1;
private int secretNumber;
private int top;
private static enum Response {YES, NO}
private Random random;
private Scanner scanner;
public static void main(String[] args) {
Game GuessingGame = new Game();
GuessingGame.start();
}
public Game() {
random = new Random( );
scanner = new Scanner(System.in);
}
public void start() {
Response answer;
answer = Response.YES;
while (answer == Response.YES) {
generateSecretNumber();
playGame();
answer = prompt("");
}
System.out.println("Bye!");
}
private void generateSecretNumber() {
secretNumber = random.nextInt(top) + 1;
System.out.println("You are going to guess a number between 1 and what number? ");
top = scanner.nextInt();
System.out.println("Type a number between 1 and: " + top);
}
private void playGame() {
int guessCount = 0;
int guess;
do {
guess = getNextGuess();
guessCount++;
if (guess < secretNumber) {
System.out.println("Too low. Try again:");
}
else if
(guess > secretNumber) {
System.out.println("Too high. Try again:");
}
}
while ( guess != secretNumber );
if ( guess == secretNumber ) {
System.out.println("Right! It took you " + guessCount + " tries");
}
else {
System.out.println("game over");
}
}
private Response prompt(String question) {
String input;
Response response = Response.NO;
System.out.print(question + "Would you like to play again? ");
input = scanner.next();
if (input.equals("Y") || input.equals("y")) {
response = Response.YES;
}
return response;
}
private int getNextGuess() {
int input;
while(true) {
System.out.print(" ");
input = scanner.nextInt();
if (LOWER_BOUND <= input && input <= top) {
return input;
}
System.out.println("Invalid input: " + "must be between " + LOWER_BOUND + " and" + top);
}
}
}
采纳答案by MForster
On first invocation topis zero, so random.nextInt(top)throws an exception. This method must only be called with positive numbers.
第一次调用时top为零，因此random.nextInt(top)抛出异常。此方法只能使用正数调用。
回答by ChristopheD
You use
你用
secretNumber = random.nextInt(top) + 1;
secretNumber = random.nextInt(top) + 1;
before tophas been assigned a meaningful value (apart from the default 0value ; random throws an exception since it needs a positive value).
beforetop已被分配一个有意义的值（除了默认0值；随机抛出异常，因为它需要一个正值）。
回答by OscarRyz
When you invoke: random.nextInt(top)at line: 44, youre passing 0 ( for that's the value of the "top" variable )
当您调用： random.nextInt(top)在第 44 行时，您传递的是 0（因为这是“top”变量的值）
You have to pass something > 0
你必须通过一些> 0
That's what the: "n must be positive"means.
这就是：“n 必须为正”的意思。
