將整數存儲到數組中，並查找素數JAVA

Question

在此交互式程序中，您將找到一個菜單，其中包含用於在陣列上執行不同功能的選項。該數組來自一個名爲「data.txt」的文件。該文件包含整數，每行一個。顯然，我沒有包括整個代碼（這太長了）。然而，我希望有人能夠幫助我解決在數組中找到素數的問題。現在，控制檯打印數組的素數地址（[I @ 4a13ccea））。歡迎任何建議。我的部分程序如下。謝謝。

public static void main(String[] args) throws FileNotFoundException { 
    Scanner sc = new Scanner(System.in); 
    System.out.println("Welcome to Calculation Program!\n"); 
    startMenus(sc); 

} 

private static void startMenus(Scanner sc) throws FileNotFoundException { 
    while (true) { 
     System.out.println("(Enter option # and press ENTER)\n"); 

     System.out.println("1. Display the average of the list"); 
     System.out.println("2. Display the number of occurences of a given element in the list"); 
     System.out.println("3. Display the prime numbers in a list"); 
     System.out.println("4. Display the information above in table form"); 
     System.out.println("5. Save the information onto a file in table form"); 
     System.out.println("6. Exit"); 

     int option = sc.nextInt(); 

     sc.nextLine(); 

     switch (option) { 
      case 1: 
       System.out.println("You've chosen to compute the average."); 
       infoMenu1(sc); 
       break; 
      case 2: 
       infoMenu2(sc, sc); 
       break; 
      case 3: 
       infoMenu3(sc); 
       break; 
      case 4: 
       infoMenu4(sc); 
       break; 
      case 5: 
       infoMenu5(sc); 
       break; 
      case 6: 
       System.exit(0); 
      default: 

       System.out.println("Unrecognized Option!\n"); 
     } 

    } 
} 
private static void infoMenu3(Scanner sc) throws FileNotFoundException { 
    File file = new File("data.txt"); 
    sc = new Scanner(file); 

    int[] numbers = new int[100]; 

    int i = 0; 

    while (sc.hasNextInt()) { 
     numbers[i] = sc.nextInt(); 
     ++i; 
    } 

    for (int j = 0; j < i; ++j) { 
     System.out.print("The numbers in the file are: " + numbers[j] + " "); 
    } 
} 
public static boolean prime(int x) { 
    boolean answer = true; 

    for (int i = 2; i <= x/2; i = i + 1) { 
     if (i != x) { 
      if (i % x == 0) { 
       answer = false; 
      } 
     } 
    } 

    return answer; 
} 

public static int[] primes(int[] numbers) { 
    int primesCount = 0; 

    for (int i : numbers) { 
     if (prime(i)) { 
      primesCount = (primesCount + 1); 
     } 
    } 

    if (primesCount == 0) { 
     return null; 
    } 

    int[] result = new int[primesCount]; 
    int index = 0; 

    for (int i : numbers) { 
     if (prime(i)) { 
      result[index] = i; 
      index = index + 1; 
     } 
    } 

    return result; 
} 
} 

Answer 1

遍歷您的陣列和打印每一個元素，或者使用java.util.Arrays.toString(int[])方法，如果其格式符合您的需求。

Answer 2

兩個標記

如果你打印一個這樣的數組，你會得到的數組，而不是內部地址。

System.out.println("The primes in the file are: " + primes(numbers)); 

替換一個循環遍歷primes(numbers)

第二個是，在你的public static boolean prime(int x)功能這一行，你這行

for (int i = 2; i <= x/2; i = i + 1) 

雖然這個工程，要找到一個黃金喲做不需要重複，直到x/2。對於性能好處x的平方根更適合。