Java中的多线程与3个线程

Question

我正在尝试创建以下程序的多线程程序来计算 Pi。我的简单程序是：

  import java.util.Random;

  public class MonteCarloPi {
    static Random generator = new Random( System.currentTimeMillis() );
    /**
     * @param args
     */
    public static void main(String[] args) {

            long N = 10000000;
            if ( args.length > 1 )
                    N = Long.parseLong( args[0] );

            double PI = myPiCompute(N);

            System.out.println( N + " random samples yield an approximation of Pi = " + PI);

    }


    public static double myPiCompute (long N){
        long Nc = 0;
            for ( long i=0; i<N; i++ ) {
                    float x = generator.nextFloat()*2 - 1; // random float in [-1,1]
                    float y = generator.nextFloat()*2 - 1; // random float in [-1,1]
                    if ( x*x + y*y <= 1.0f )
                            Nc += 1;
            }

            double PI = 4.0*Nc/N;
            return PI;
    }

}

现在，我正在尝试使其成为多线程（至少 3 个线程）。所以我正在执行以下操作但遇到错误。

 import java.util.Random;

   class MyThread implements Runnable {
    /**
     * @param args
     */
    static Random generator = new Random( System.currentTimeMillis() );
        public void run() {
            System.out.println("this thread is running ... ");
            long N = 10000000;
            if ( args.length > 1 )
                    N = Long.parseLong( args[0] );
            double PI = myPiCompute(N);

            System.out.println( N + " random samples yield an approximation of Pi = " + PI);

        }
    }


    public static double myPiCompute (long N){
        long Nc = 0;
            for ( long i=0; i<N; i++ ) {
                    float x = generator.nextFloat()*2 - 1; // random float in [-1,1]
                    float y = generator.nextFloat()*2 - 1; // random float in [-1,1]
                    if ( x*x + y*y <= 1.0f )
                            Nc += 1;
            }

            double PI = 4.0*Nc/N;
            return PI;
    }




public class MonteCarloPi {

        public static void main(String[] args) {

                MyThread myObject = new MyThread();
                Thread thr1 = new Thread(myObject);
                thr1.start();

                Thread thr2 = new Thread(myObject);
                thr2.start();

                Thread thr3 = new Thread(myObject);
                thr3.start();
    }

  }

我收到以下错误。

     MonteCarloPiPar.java:19: error: class, interface, or enum expected
    public static double myPiCompute (long N){
                  ^
    MonteCarloPiPar.java:21: error: class, interface, or enum expected
            for ( long i=0; i<N; i++ ) {
            ^
    MonteCarloPiPar.java:21: error: class, interface, or enum expected
            for ( long i=0; i<N; i++ ) {
                            ^
    MonteCarloPiPar.java:21: error: class, interface, or enum expected
            for ( long i=0; i<N; i++ ) {
                                 ^
     MonteCarloPiPar.java:23: error: class, interface, or enum expected
                    float y = generator.nextFloat()*2 - 1; // random float in [-1,1]
                    ^
    MonteCarloPiPar.java:24: error: class, interface, or enum expected
                    if ( x*x + y*y <= 1.0f )
                    ^
     MonteCarloPiPar.java:26: error: class, interface, or enum expected
            }
            ^
    MonteCarloPiPar.java:29: error: class, interface, or enum expected
            return PI;
            ^
    MonteCarloPiPar.java:30: error: class, interface, or enum expected
    }
    ^
   9 errors

我正在尝试使用多线程进行游戏。谁能指出我做错了什么。

Answer 1

错误抛出行上方有一个额外的右大括号。

这里：

class MyThread implements Runnable {
    public void run() {
        System.out.println("this thread is running ... ");
        long N = 10000000;
        if ( args.length > 1 )
                N = Long.parseLong( args[0] );
        double PI = myPiCompute(N);

        System.out.println( N + " random samples yield an approximation of Pi = " + PI);

    }
}  // <<< *********

摆脱它，然后删除这个问题。将来，当这种情况发生时，计算您的左大括号和右大括号。

Answer 2

你的“myPiCompute”函数不在一个类中。