Parallel works as long as numUsers >= numPrinters

src/part3/aufg2/Schlenglein.java

@@ -38,6 +38,10 @@ public class Schlenglein <T>{
         return this.maxSize;
     }
 
+    public boolean isEmpty(){
+        return this.size()<=0;
+    }
+
     public void attemptDynamicResize(){
         if (numberOfElements < 0.2*maxSize){
             // Kleiner Machen

src/part4/aufg2/Demo.java

@@ -9,11 +9,20 @@ Zwei Drucker stehen zur Verfügung und arbeiten die Aufträge ab.
 Modellieren Sie das Problem als Erzeuger‐Verbraucher‐Problem und realisieren Sie es in Java.
  */
 
+
 public class Demo {
     public static void main(String[] args) {
-        User u1 = new User(1);
-        User u2 = new User(2);
-        u1.start();
-        u2.start();
+        int numUsers = 7;
+        int numPrinter = 4;
+
+        for (int i = 1; i <= numUsers; i++) {
+            User user = new User(i);
+            user.start();
+        }
+
+        for (int i = 1; i <= numPrinter ; i++) {
+            Printer printer = new Printer(i);
+            printer.start();
+        }
     }
 }

src/part4/aufg2/Printer.java

@@ -1,18 +1,31 @@
 package part4.aufg2;
 
-import part3.aufg2.Schlenglein;
+public class Printer extends Thread {
+    private int threadNumber;
 
-public class Printer {
-    static Schlenglein q;
+    public Printer(int threadNumber){
+        this.threadNumber = threadNumber;
+    }
 
-    public void run(){
-        synchronized (getClass()){
+    public void run() {
+        while (true) {
             try {
-                q.wait();
-            } catch (InterruptedException e) {
-                throw new RuntimeException(e);
+                synchronized (Puwwer.q) {
+                    if (Puwwer.q.isEmpty()){
+                        try {
+                            Puwwer.q.wait();
+                        } catch (InterruptedException e) {
+                            throw new RuntimeException(e);
+                        }
+                    }
+                    System.out.println("Printer " + this.threadNumber + " prints " + Puwwer.q.get());
+                }
+            } catch (NullPointerException e){}
+            try {
+                sleep(100);
+            } catch (InterruptedException ex) {
+                throw new RuntimeException(ex);
             }
-
         }
     }
 }

src/part4/aufg2/Puwwer.java

@@ -0,0 +1,7 @@
+package part4.aufg2;
+
+import part3.aufg2.Schlenglein;
+
+public class Puwwer {
+    static Schlenglein q = new Schlenglein();
+}

src/part4/aufg2/User.java

@@ -1,40 +1,36 @@
 package part4.aufg2;
 
-import part3.aufg2.Schlenglein;
-
-
-
-public class User <T> extends Thread {
+public class User extends Thread {
     private int threadNumber;
-    static Schlenglein q = new Schlenglein<String>();
-
     public User(int threadNumber) {
         this.threadNumber = threadNumber;
     }
 
     public synchronized void makeRequest() {
-        synchronized (getClass()) {
+        synchronized (Puwwer.q) {
             int randomInt = (int) (Math.random() * ((int) (Math.random() * 1000)));
             String randomIntStr = this.threadNumber + " " + randomInt;
-            q.add(randomIntStr);
-            q.printAll();
+
+            Puwwer.q.add(randomIntStr);
+
+            System.out.println("User " + threadNumber + " added " + randomIntStr);
+
+            try {
+                Puwwer.q.notify();
+            } catch (IllegalMonitorStateException e) {
+                throw new RuntimeException(e);
+            }
         }
     }
 
     public void run() {
-
-            try {
-               // q.notify();
-            } catch (IllegalMonitorStateException e) {
-                throw new RuntimeException(e);
-            }
-            for (int i = 0; i<10; i++) {
+            while (true) {
                 makeRequest();
                 try {
-                    sleep(100);
+                    sleep(3000);
                 } catch (InterruptedException e) {
                     throw new RuntimeException(e);
+               }
             }
-        }
     }
 }