HangMan RandomString类 [英] HangMan RandomString Class

问题描述

可能重复：

Java RandomString类

以下是方向：

创建一个 RandomString 类，并执行以下操作：

1. 创建一个名为guess_phrases.txt的文件，其中包含您的Hangman游戏中要猜到的短语。该文件每行将有一个猜测短语。




2. 一个构造函数，它接收文件的名称以获取字符串值。构造函数应该从文件中读取短语并存储以备以后使用。




3. 从文件返回随机字符串值的方法;这个值不应该重复，直到文件中的所有猜测短语都被使用为止。

创建一个主要方法测试下一个工作是否正确通过重复调用next&打印结果 - 您不应该有任何重复，短语不应该与文件中的顺序相同。

我创建了一个名为的文件guess_phrases带有随机短语的.txt 当我运行这个我收到一个错误，也不是随机打印，为什么这样？如何解决这个问题？

错误
线程main中的异常java.lang.IllegalArgumentException：n必须为正值

 在java.util.Random.nextInt（未知来源）
在RandomString.next（RandomString.java:32）
在RandomString。 main（RandomString.java:40）
  

这是我在RandomString类中有的

  public class RandomString {
 
随机随机= new Random（）; 
 ArrayList< String> guessPhrases = new ArrayList< String>（）; 
扫描仪fileScan; 
 
 public RandomString（String guessPhrases）throws FileNotFoundException {
 
 //创建一个Scanner对象从文件中读取
 fileScan = new Scanner（new File（guess_phrases 。文本））; 
 
 //将所有短语从文件添加到ArrayList 
 while（fileScan.hasNext（））{
 
 String line = guessPhrases.nextLine（） ; // get input 
 System.out.println（line）; // print line 
 guessPhrases.add（line）; //添加行到数组列表
} 
} 
 
 public String next（）{
 int i = random.nextInt（guessPhrases.size（））; 
 return guessPhrases.get（i）; 
} 
 
 public static void main（String [] args）{
 
} 
} 
  / pre> 
 
解决方案
从 随机API   
 
 
 
你可以看到，如果你将一个negetive数字传递给nextInt（pos），它会抛出一个 IllegalArgumentException  
 
 
 
 int i = random。 nextInt（guessPhrases.size（））; 
 
 
 
绝对 guessPhrases.size（）是 / strong>，因此例外
 

  
Possible Duplicate:

  Java RandomString Class  
Here are the directions:

Create a RandomString class and implement the following:

Create a file named guess_phrases.txt that contains phrases to be guessed in your Hangman game. This file will have one guess phrase per line. 
A constructor that receives the name of a file to get string values from. The constructor should read in the phrases from the file and store them for later use. 
A method that returns a random string value from the file; this value shouldn't be repeated until all guess phrases in the file have been used.
Create a main method to test that next is working correctly by repeatedly calling next & printing the result – you should not have any repeats, and the phrases should not be in the same order as in the file.

I created a file called guess_phrases.txt with random phrases. When I run this I get an error, also it is not printed randomly, why is this? How can I fix this ?

error
Exception in thread "main" java.lang.IllegalArgumentException: n must be positive
at java.util.Random.nextInt(Unknown Source)
at RandomString.next(RandomString.java:32)
at RandomString.main(RandomString.java:40)
This is what I have in the RandomString Class
public class RandomString {

    Random random = new Random();
    ArrayList<String> guessPhrases = new ArrayList<String>();
    Scanner fileScan;

    public RandomString(String guessPhrases) throws FileNotFoundException {

        // create a Scanner object to read from the file
        fileScan = new Scanner(new File("guess_phrases.txt"));

        // add all of the phrases from the file into the ArrayList
        while (fileScan.hasNext()) {

            String line = guessPhrases.nextLine(); // get input
            System.out.println(line); // print line
            guessPhrases.add(line); // add line to array list
        }
    }

    public String next() {
        int i = random.nextInt(guessPhrases.size());
        return guessPhrases.get(i);
    }

    public static void main(String[] args) {

    }
}

解决方案
From Random API

you can see that if you pass a negetive number or zero to nextInt(pos) it will throw an IllegalArgumentException  

        int i = random.nextInt(guessPhrases.size());

Most definitely guessPhrases.size() is zero, thus the Exception

                        
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