Vorlesung 13 / Aufgabe 2

VL13/Aufgabe02/Aufgabe02.java

@@ -0,0 +1,23 @@
+package VL13.Aufgabe02;
+
+public class Aufgabe02 {
+  public static void main(String[] args) {
+    MyQueue<Integer> integerQueue = new MyQueue<Integer>();
+
+    // fill the queue with some values.
+    System.out.printf("\n%s:\n", "Aufbau der Queue");
+
+    for (int i = 0; i < 150; i++) {
+      integerQueue.add(i);
+      System.out.printf("Elemente: %d - Größe: %d\n", integerQueue.size(), integerQueue.internalSize());
+    }
+
+    // clear the queue to check the resizing of the internal storage.
+    System.out.printf("\n%s:\n", "Abbau der Queue");
+
+    while (integerQueue.size() > 0) {
+      integerQueue.get();
+      System.out.printf("Elemente: %d - Größe: %d\n", integerQueue.size(), integerQueue.internalSize());
+    }
+  }
+}

VL13/Aufgabe02/MyQueue.java

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+package VL13.Aufgabe02;
+
+public class MyQueue<T> {
+  private Object[] myArray;
+  private int numberOfElements;
+  private int maxSize;
+
+  public MyQueue() {
+    this.numberOfElements = 0;
+    this.maxSize = 100;
+    myArray = new Object[this.maxSize];
+  }
+
+  public void add(T t) {
+    this.myArray[this.numberOfElements] = t;
+    this.numberOfElements++;
+    this.adjustInternalArray();
+  }
+
+  public T get() {
+    T retValue = (T) this.myArray[0];
+
+    for (int i = 0; i < this.numberOfElements; i++) {
+      this.myArray[i] = this.myArray[i + 1];
+    }
+
+    this.numberOfElements--;
+    this.adjustInternalArray();
+    return retValue;
+  }
+
+  public int size() {
+    return this.numberOfElements;
+  }
+
+  public int internalSize() {
+    return this.maxSize;
+  }
+
+  private void adjustInternalArray() {
+    final int MIN_SIZE = 20;
+
+    while (this.numberOfElements <= Math.ceil(this.maxSize * 0.2) && this.maxSize > MIN_SIZE) {
+      this.maxSize = Math.max(this.maxSize / 2, 20);
+      Object[] myOldArray = this.myArray;
+      this.myArray = new Object[this.maxSize];
+
+      for (int i = 0; i < this.myArray.length; i++) {
+        this.myArray[i] = myOldArray[i];
+      }
+    }
+
+    while (this.numberOfElements >= Math.ceil(this.maxSize * 0.8)) {
+      this.maxSize = this.maxSize * 2;
+      Object[] myOldArray = this.myArray;
+      this.myArray = new Object[this.maxSize];
+
+      for (int i = 0; i < myOldArray.length; i++) {
+        this.myArray[i] = myOldArray[i];
+      }
+    }
+  }
+}