計數器給隨機數

我想實現一個計劃，將讓學生從1數 - 10計數器給隨機數

以下是我的代碼：

主要類：

public class JavaLab5 { 
    public static final int DEBUG = 0; 

    public static void multipleThreads(int number) { 
     StudentThread []st = new StudentThread[number]; 
     for (int loop = 0; loop < number;loop++) { 
      st[loop] = new StudentThread(); 
      st[loop].start(); 
     } 
    } 
    /** 
    * @param args the command line arguments 
    */ 
    public static void main(String[] { 
     multipleThreads(10); 
    } 
}

Student類：

public class Student { 
    static int studentCounter = 1; 
    String name; 
    private static int count = 0; 
    public static int instances = 0; 

    // Getters 
    /** 
    * 
    * @return 
    */ 
    public String getName() { 
     return this.name; 
    } 

    // Setters 
    /** 
    * 
    * @param name 
    */ 
    public void setName(String name) { 
     if (JavaLab5.DEBUG > 3) System.out.println("In Student.setName. Name = "+ name); 
     this.name = name; 
    } 

    /** 
    * Default constructor. 
    * Populates name with defaults 
    */ 
    public Student() { 
     instances++; 
     this.name = "Not Set"; 
    } 

    /** 
    * Constructor with parameters 
    * @param name String with the name 
    */ 
    public Student(String name) { 
     this.name = name; 
    } 

    /** 
    * Destructor 
    * @throws Throwable 
    */ 
    protected void finalize() throws Throwable { 
     //do finalization here 
     instances--; 
     super.finalize(); //not necessary if extending Object. 
    } 

    /** 
    * @return 
    */ 
    public void getCounter() { 
     count++; 
     //return count; 
     System.out.println(count); 
    } 

    @Override 
    public String toString() { 
     return this.name; 
    } 

    /** 
    * 
    * @return 
    */ 
    public String getSubjects() { 
     return null; 
    } 
}

計算機學生類：

public class ComputerStudent extends Student { 
    int studCountObj; 

    /** 
    * Default constructor 
    */ 
    public ComputerStudent() { 
     super(); 
    } 

    public ComputerStudent(String name) { 
     super(name); 
     studCountObj=studentCounter; 
     studentCounter++; 
    } 

    /** 
    * Display information about the subject 
    * @return 
    */ 
    @Override 
    public String getSubjects(){ 
     return(" Computer Student" + "[" + studCountObj + "] " + name + ": "); 
    } 
}

科學學生：

public class ScienceStudent extends Student { 
    int studCountObj; 

    /** 
    * Default constructor 
    */ 
    public ScienceStudent() { 
     super(); 
    } 

    public ScienceStudent(String name) { 
     super(name); 
     studCountObj=studentCounter; 
     studentCounter++; 
    } 

    /** 
    * Display information about the subject 
    * @return 
    */ 
    @Override 
    public String getSubjects(){ 
     return(" Science Student" + "[" + studCountObj + "]" + "-" + name + ": "); 
    } 
}

數學的學生：

public class MathStudent extends Student { 
    int studCountObj; 

    /** 
    * Default constructor 
    * @param name 
    */ 
    public MathStudent(String name) { 
     super(name); 
     studCountObj=studentCounter; 
     studentCounter++; 
    } 

    public MathStudent() { 
     super(); 
    } 

    /** 
    * Display information about the subject 
    * @return 
    */ 
    @Override 
    public String getSubjects(){ 
     return(" MathStudent" + "[" + studCountObj + "]" + "-" + name + ": "); 
    } 
}

學生主題：

public class StudentThread extends Thread { 

    @Override 
    public void run(){ 
     Student s[] = new Student[10]; 

     //Student Array containing different types of students 
     s[0] = new MathStudent("Smith"); 
     s[1] = new MathStudent("Jack"); 
     s[2] = new MathStudent("Victor"); 
     s[3] = new MathStudent("Mike"); 
     s[4] = new ScienceStudent("Dave"); 
     s[5] = new ScienceStudent("Oscar"); 
     s[6] = new ScienceStudent("Peter"); 
     s[7] = new ComputerStudent("Philip"); 
     s[8] = new ComputerStudent("Shaun"); 
     s[9] = new ComputerStudent("Scott"); 

     //Checking and looping till the count reaches 10 
     //for (int j = 0; j < 10; j++) { 
      //Checking and looping till the end of the student array 
      for (int i = 0; i < s.length; i++) { 
       System.out.println(); 
       System.out.print(s[i].getSubjects() + " - " + "Count:"); 
       s[i].getCounter(); 
     } 
     try { 
     Thread.sleep(1000); 
     } catch (InterruptedException e) { 
     System.out.println("Exception at StudentThread.run: " + e); 
     } 
     } 

}

當前代碼的輸出提供：

MathStudent[12]-Smith: - Count: 
MathStudent[28]-Smith: - Count:2 




MathStudent[1]-Smith: - Count:3 




MathStudent[20]-Smith: - Count:4 

MathStudent[21]-Jack: - Count:5 

MathStudent[16]-Smith: - Count:6 

MathStudent[2]-Jack: - Count:7 

MathStudent[36]-Smith: - Count:8 

MathStudent[24]-Smith: - Count:9 

MathStudent[25]-Jack: - Count:10 

MathStudent[26]-Victor: - Count:11 

MathStudent[27]-Mike: - Count:12 

Science Student[52]-Dave: - Count:13 
MathStudent[37]-Jack: - Count:14 

MathStudent[38]-Victor: - Count:15 

MathStudent[39]-Mike: - Count: MathStudent[29]-Jack: - Count:17 

1 

MathStudent[13]-Jack: - Count:18 

MathStudent[14]-Victor: - Count:19 

MathStudent[30]-Victor: - Count:20 

MathStudent[32]-Smith: - Count:21 

MathStudent[1]-Smith: - Count:22 

MathStudent[33]-Jack: - Count:23 

MathStudent[31]-Mike: - Count:24 

MathStudent[15]-Mike: - Count:25 

Science Student[64]-Dave: - Count:26 

Science Student[65]-Oscar: - Count:27 

Science Student[66]-Peter: - Count:28 

16 
Computer Student[67] Philip: - Count:29 


MathStudent[4]-Victor: - Count:30 

MathStudent[17]-Jack: - Count:31 

MathStudent[18]-Victor: - Count:32 

MathStudent[19]-Mike: - Count:33 

MathStudent[22]-Victor: - Count:34 

MathStudent[8]-Smith: - Count:35 

MathStudent[9]-Jack: - Count:36 

MathStudent[10]-Victor: - Count:37 

MathStudent[11]-Mike: - Count:38 

MathStudent[23]-Mike: - Count:39 

Science Student[61]-Dave: - Count:40 

MathStudent[6]-Mike: - Count:41 

Science Student[46]-Dave: - Count:42 

Science Student[53]-Oscar: - Count:43 

Computer Student[70] Shaun: - Count:44 

Computer Student[73] Scott: - Count:45 

Science Student[55]-Dave: - Count:46 

Science Student[56]-Oscar: - Count:47 

MathStudent[34]-Victor: - Count:48 

MathStudent[35]-Mike: - Count:49 

Science Student[41]-Dave: - Count:50 

MathStudent[3]-Jack: - Count:51 

Science Student[43]-Oscar: - Count:52 

Science Student[44]-Peter: - Count:53 

Science Student[57]-Peter: - Count:54 

Science Student[49]-Dave: - Count:55 

Science Student[50]-Oscar: - Count:56 

Science Student[51]-Peter: - Count:57 

Computer Student[97] Philip: - Count:58 

Computer Student[98] Shaun: - Count:59 

Computer Student[99] Scott: - Count:60 
Science Student[54]-Peter: - Count:61 

Computer Student[88] Philip: - Count:62 

Computer Student[89] Shaun: - Count:63 

Computer Student[90] Scott: - Count:64 
Science Student[47]-Oscar: - Count:65 

Science Student[48]-Peter: - Count:66 

Computer Student[76] Philip: - Count:67 

Computer Student[77] Shaun: - Count:68 

Computer Student[78] Scott: - Count:69 
Science Student[62]-Oscar: - Count:70 

Science Student[63]-Peter: - Count:71 

Computer Student[79] Philip: - Count:72 

Computer Student[80] Shaun: - Count:73 

Science Student[58]-Dave: - Count:74 

Science Student[59]-Oscar: - Count:75 

Science Student[60]-Peter: - Count:76 

Science Student[68]-Dave: - Count:77 

Computer Student[82] Philip: - Count:78 

Computer Student[81] Scott: - Count:79 
Computer Student[85] Philip: - Count:80 

Computer Student[86] Shaun: - Count:81 

Computer Student[94] Philip: - Count:82 

MathStudent[5]-Victor: - Count:83 

Computer Student[95] Shaun: - Count:84 

Computer Student[87] Scott: - Count:85 
Computer Student[83] Shaun: - Count:86 

Science Student[69]-Oscar: - Count:87 

Computer Student[84] Scott: - Count:88 
Computer Student[96] Scott: - Count:89 
MathStudent[7]-Mike: - Count:90 

Science Student[71]-Peter: - Count:91 

Science Student[40]-Dave: - Count:92 

Science Student[42]-Oscar: - Count:93 

Computer Student[72] Philip: - Count:94 

Science Student[45]-Peter: - Count:95 

Computer Student[91] Philip: - Count:96 

Computer Student[74] Shaun: - Count:97 

Computer Student[92] Shaun: - Count:98 

Computer Student[93] Scott: - Count:99 
Computer Student[75] Scott: - Count:100

正如你所看到的，當前的輸出給出了randon計數值和隨機的學生值，我不明白爲什麼。

，我需要的輸出是：

MathStudent[1]-Smith: - Count:1 
MathStudent[2]-Jack: - Count:1 
MathStudent[3]-Victor: - Count:1 
MathStudent[4]-Mike: - Count:1 
Science Student[5]-Dave: - Count:1 
Science Student[6]-Oscar: - Count:1 
Science Student[7]-Peter: - Count:1 
Computer Student[8] Philip: - Count:1 
Computer Student[9] Shaun: - Count:1 
Computer Student[10] Scott: - Count:1 
MathStudent[1]-Smith: - Count:2 
MathStudent[2]-Jack: - Count:2 
MathStudent[3]-Victor: - Count:2 
MathStudent[4]-Mike: - Count:2 
Science Student[5]-Dave: - Count:2 
Science Student[6]-Oscar: - Count:2 
Science Student[7]-Peter: - Count:2 
Computer Student[8] Philip: - Count:2 
Computer Student[9] Shaun: - Count:2 
Computer Student[10] Scott: - Count:2 
MathStudent[1]-Smith: - Count:3 
MathStudent[2]-Jack: - Count:3 
MathStudent[3]-Victor: - Count:3 
MathStudent[4]-Mike: - Count:3 
Science Student[5]-Dave: - Count:3 
Science Student[6]-Oscar: - Count:3 
Science Student[7]-Peter: - Count:3 
Computer Student[8] Philip: - Count:3 
Computer Student[9] Shaun: - Count:3 
Computer Student[10] Scott: - Count:3 
MathStudent[1]-Smith: - Count:4 
MathStudent[2]-Jack: - Count:4 
MathStudent[3]-Victor: - Count:4 
MathStudent[4]-Mike: - Count:4 
Science Student[5]-Dave: - Count:4 
Science Student[6]-Oscar: - Count:4 
Science Student[7]-Peter: - Count:4 
Computer Student[8] Philip: - Count:4 
Computer Student[9] Shaun: - Count:4 
Computer Student[10] Scott: - Count:4 
MathStudent[1]-Smith: - Count:5 
MathStudent[2]-Jack: - Count:5 
MathStudent[3]-Victor: - Count:5 
MathStudent[4]-Mike: - Count:5 
Science Student[5]-Dave: - Count:5 
Science Student[6]-Oscar: - Count:5 
Science Student[7]-Peter: - Count:5 
Computer Student[8] Philip: - Count:5 
Computer Student[9] Shaun: - Count:5 
Computer Student[10] Scott: - Count:5 
MathStudent[1]-Smith: - Count:6 
MathStudent[2]-Jack: - Count:6 
MathStudent[3]-Victor: - Count:6 
MathStudent[4]-Mike: - Count:6 
Science Student[5]-Dave: - Count:6 
Science Student[6]-Oscar: - Count:6 
Science Student[7]-Peter: - Count:6 
Computer Student[8] Philip: - Count:6 
Computer Student[9] Shaun: - Count:6 
Computer Student[10] Scott: - Count:6 
MathStudent[1]-Smith: - Count:7 
MathStudent[2]-Jack: - Count:7 
MathStudent[3]-Victor: - Count:7 
MathStudent[4]-Mike: - Count:7 
Science Student[5]-Dave: - Count:7 
Science Student[6]-Oscar: - Count:7 
Science Student[7]-Peter: - Count:7 
Computer Student[8] Philip: - Count:7 
Computer Student[9] Shaun: - Count:7 
Computer Student[10] Scott: - Count:7 
MathStudent[1]-Smith: - Count:8 
MathStudent[2]-Jack: - Count:8 
MathStudent[3]-Victor: - Count:8 
MathStudent[4]-Mike: - Count:8 
Science Student[5]-Dave: - Count:8 
Science Student[6]-Oscar: - Count:8 
Science Student[7]-Peter: - Count:8 
Computer Student[8] Philip: - Count:8 
Computer Student[9] Shaun: - Count:8 
Computer Student[10] Scott: - Count:8 
MathStudent[1]-Smith: - Count:9 
MathStudent[2]-Jack: - Count:9 
MathStudent[3]-Victor: - Count:9 
MathStudent[4]-Mike: - Count:9 
Science Student[5]-Dave: - Count:9 
Science Student[6]-Oscar: - Count:9 
Science Student[7]-Peter: - Count:9 
Computer Student[8] Philip: - Count:9 
Computer Student[9] Shaun: - Count:9 
Computer Student[10] Scott: - Count:9 
MathStudent[1]-Smith: - Count:10 
MathStudent[2]-Jack: - Count:10 
MathStudent[3]-Victor: - Count:10 
MathStudent[4]-Mike: - Count:10 
Science Student[5]-Dave: - Count:10 
Science Student[6]-Oscar: - Count:10 
Science Student[7]-Peter: - Count:10 
Computer Student[8] Philip: - Count:10 
Computer Student[9] Shaun: - Count:10 
Computer Student[10] Scott: - Count:10

爲什麼輸出打印出隨機計數值和隨機學生人數，以及如何我，我可以解決這個問題？

來源

2017-03-23 madman123

您需要在線程之間共享同步更新計數器，或使用'AtomicInteger'。 –

您可以按照[這裏]指導（http://stackoverflow.com/help/mcve）自行修復它。在最小化你的例子的過程中，你無疑會發現問題。 –

你預計這個循環何時結束？ 'for（int loop = 0; loop Andreas

count和StudentCounter是靜態變量。因此，它們由所有學生對象更新。你開始10，並在每個線程instanciate 10學生。這100個學生實例中的每一個更新這些變量，這些變量在所有實例中被共享，因爲它們被聲明爲靜態的。

來源

2017-03-23 21:56:25 Lunar

但是，如果我不聲明它是靜態的，它只是讓所有學生的學號爲1，不增加。 – madman123

您應該在學生對象中創建一個ID字段，並在創建時或之後進行分配。 – Lunar

不明白？ – madman123

對於Java提供的AtomicInteger這種問題，女巫以原子方式執行Integer操作。

只需更換爲您的AtomicInteger靜態INT變量，然後使用類的方法：

https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/atomic/AtomicInteger.html

來源

2017-03-27 05:49:32

計數器給隨機數

回答

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