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Thread: PipeInputStream & PipeOutputStream

  1. #1
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    Default PipeInputStream & PipeOutputStream

    is it possible for One PipeInputStream to stream out to two PipeOutputStream? I am trying to get the third thread to from Pipe 2 to read the first thread from Pipe 1.

    The class displayInfo is the problem for me below. It read 3 variable TWICE, before it can print out the results on the second time. Please help me fix it.

    // Example showing how to pass data from one thread to another
    // through a pipe, for the Quadratic Equation Solver.
     
    //import java.util.*;
    import java.io.*;
     
    public class assign2 {
     
    	public static void main(String args[]) {
     
    		try {
    			PipedOutputStream out1 = new PipedOutputStream();
    			PipedInputStream in1 = new PipedInputStream(out1);
    			PipedOutputStream out2 = new PipedOutputStream();
    			PipedInputStream in2 = new PipedInputStream(out2);
     
    			readCoeffs prod = new readCoeffs(out1);
    			calRoots filt = new calRoots(in1, out2);
    			displayInfo cons = new displayInfo(in1, in2);
     
    			cons.start();
    			prod.start();
    			filt.start();
    		} catch (IOException e) {
    		}
    	}
     
    }
     
    class readCoeffs extends Thread {
    	private DataOutputStream out;
    	private int count = 1;
    	double[] readers = new double[3];
    	BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
     
    	public readCoeffs(OutputStream os) {
    		out = new DataOutputStream(os);
    	}
     
    	public void run() {
    		while (true) {
    			try {
    				if (count > 3) {
    					count = 1;
    				}
    				for (int i = 0; i < 3; i++) {
    					System.out.print("Please enter coefficient #" + count + ": ");
    					readers[i] = Double.parseDouble(input.readLine());
    					System.out.println("Passing coefficient #" + count + " into a pipe.");
    					count++;
    					out.writeDouble(readers[i]);
    				}
    				out.flush();
    				sleep(1000);
    			} catch (Exception e) {
    				System.out.println("readCoeffs ERROR: " + e);
    			}
    		}
    	}
    }
     
    class calRoots extends Thread {
    	private DataInputStream in;
    	private DataOutputStream out;
    	double[] readersin = new double[3];
    	double[] roots = new double[2];
     
    	public calRoots(InputStream is, OutputStream os) {
    		in = new DataInputStream(is);
    		out = new DataOutputStream(os);
    	}
     
    	public void run() {
    		for (;;) {
    			try {
    				for (int i = 0; i < 3; i++) {
    					readersin[i] = in.readDouble();
    				}
     
    				double a = readersin[0];
    				double b = readersin[1];
    				double c = readersin[2];
    				System.out.println("\t(2) >>>Root calculating thread...");
     
    				if (b * b - 4 * a * c >= 0.0) {
    					roots[0] = (-b - Math.sqrt(b * b - 4 * a * c)) / (2.0 * a);
    					roots[1] = (-b + Math.sqrt(b * b - 4 * a * c)) / (2.0 * a);
    					out.writeDouble(roots[0]);
    					out.writeDouble(roots[1]);
    					out.flush();
    				} else {
    					out.writeDouble(0.0);
    					out.writeDouble(0.0);
    				}
    				System.out.println("\t(2) Root solver passed...");
    			} catch (IOException e) {
    				System.out.println("calRoots ERROR: " + e);
    			}
    		}
    	}
    }
     
    class displayInfo extends Thread {
    	private DataInputStream in1;
    	private DataInputStream in2;
    	double[] readersin = new double[3];
    	double[] avg = new double[2];
     
    	public displayInfo(InputStream is1, InputStream is2) {
    		in1 = new DataInputStream(is1);
    		in2 = new DataInputStream(is2);
    	}
     
    	public void run() {
    		for (;;) {
    			try {
    				for (int i = 0; i < 3; i++) {
    					readersin[i] = in1.readDouble();
    				}
    				double a = readersin[0];
    				double b = readersin[1];
    				double c = readersin[2];
     
    				for (int i = 0; i < 2; i++) {
    					avg[i] = in2.readDouble();
    				}
    				double root1 = avg[0];
    				double root2 = avg[1];
     
    				System.out.println("For coefficients");
    				System.out.println("a: " + a + ", b: " + b + ", c: " + c);
    				System.out.println("\t\t(3) >>>Consuming the roots...");
    				System.out.println("\t\t(3) Displaying root #1: " + root1);
    				System.out.println("\t\t(3) Displaying root #2: " + root2);
    			} catch (IOException e) {
    				System.out.println("Error3: " + e);
    			}
    		}
    	}
    }


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: PipeInputStream & PipeOutputStream

    Can you post the contents of the console from when you execute the program that shws your input and the programs output. Add some comments to the post to show what the output should be or to show where the error is.

    To make for easier testing, put the input into the program. Change the StringReader on the following line to be the program's input:
           StringReader sr = new StringReader("3\n34\n56\n78\n12\n23\n34\n");
    	BufferedReader input = new BufferedReader(sr); //new InputStreamReader(System.in));
    Last edited by Norm; September 25th, 2012 at 05:56 PM.
    If you don't understand my answer, don't ignore it, ask a question.