我將如何得到不使用`import java.util.Random`的重複結果？

Question

美好的一天！我是編程的初學者，我一直在編寫一個程序。它使用import java.util.Random，因爲我希望我的問題以任意順序隨機出現。但問題和唯一的問題是這個問題重複。例如，「你快樂嗎？」被問了三次，「你想要iPhone 5嗎？」甚至沒有被問到。我應該怎麼做才能以不特定的順序顯示所有問題，因此它不會多次選擇相同的問題？到目前爲止，這就是我所擁有的。

import java.util.Random; 
public class RandomQuiz { 
    public static void main (String args []){ 
     int a, b=0; 
     String arr []; 
     arr = new String [5]; 
     a = b; 
     arr [a] = "Are you happy? \na. yes\t\tb. no\nc. maybe\td. no comment"; 
     a = b+1; 
     arr [a] = "Did you eat breakfast? \na. yes\t\tb. no\nc. maybe\td. no comment"; 
     a = b+2; 
     arr [a] = "Have you watched tv? \na. yes\t\tb. no\nc. maybe\td. no comment"; 
     a = b+3; 
     arr [a] = "Do you want iPhone 5? \na. yes\t\tb. no\nc. maybe\td. no comment"; 
     a = b+4; 
     arr [a] = "Will you have iPad mini? \na. yes\t\tb. no\nc. maybe\td. no comment"; 

     //prints array values in random 
     Random randnum = new Random(); 
     for (int count = 1; count <=5; count++){ 
      a = randnum.nextInt (5); 
      System.out.println ("Question # " + count + "\n" + arr [a]); 
     } 
    } 
} 

Answer 1

試試這個

Random randnum = new Random (System.currentTimeMillis()); 
    java.util.HashSet<Integer> myset = new java.util.HashSet<Integer>(); 
    for (int count = 1; count <=5; count++){ 
     while(true) { 
      a = randnum.nextInt (5) ; 
      if(!myset.contains(a)) { myset.add(new Integer(a)); break;} 
     } 
     System.out.println ("Question # " + count + "\n" + arr [a]); 
    } 

Answer 2

1和5之間的真正的隨機整數幾乎肯定會有重複的數字的大量。如果你只想把數組的元素以隨機的順序，那麼你應該使用Collections.shuffle：

public static void main(String[] args) { 
    String[] array = { 
    "Are you happy? \na. yes\t\tb. no\nc. maybe\td. no comment", 
    "Did you eat breakfast? \na. yes\t\tb. no\nc. maybe\td. no comment", 
    "Have you watched tv? \na. yes\t\tb. no\nc. maybe\td. no comment", 
    "Do you want iPhone 5? \na. yes\t\tb. no\nc. maybe\td. no comment", 
    "Will you have iPad mini? \na. yes\t\tb. no\nc. maybe\td. no comment" 
    }; 

    List<String> items = Arrays.asList(array); 
    Collections.shuffle(items); 

    for (int index = 0; index < 5; index++) { 
    System.out.println("Question # " + (index + 1) + "\n" + items.get(index)); 
    } 
}