SS 2025

2025_Praxis_der_Programmierung/Verweise.java

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+/**
+ * Verweise.java
+ * 
+ * Ein Programm, das die Funktionsweise von Verweisen demonstriert.
+ */
+
+class Verweise {
+
+  public static void main(String[] args) {
+
+    // Definitionen
+    Point p1, p2;
+
+    // Initialisieren
+
+    p1 = null;
+    p2 = new Point();
+
+    System.out.println();
+    System.out.println("Die Werte der Referenzvariablen sind:");
+    System.out.println();
+    System.out.println("   p1 = " + p1);
+    System.out.println("   p2 = " + p2);
+    System.out.println();
+
+    // Das kann zur Zeit nicht gut gehen:
+    // System.out.println(" p1 = (" + p1.x + "," + p1.y + ")");
+
+    // Erzeugen von p1 und Verschieben von p2
+
+    p1 = new Point();
+    p2.moveTo(2, 3);
+
+    System.out.println();
+    System.out.println("Klassen sind Referenz-Datentypen:");
+    System.out.println();
+    System.out.println("   p1 = " + p1);
+    System.out.println("   p2 = " + p2);
+    System.out.println();
+
+    System.out.println("   p1 = (" + p1.x + "," + p1.y + ")");
+    System.out.println("   p2 = (" + p2.x + "," + p2.y + ")");
+    System.out.println();
+
+    System.out.println("Jetzt wird p2 = p1 gesetzt.");
+    System.out.println();
+
+    p2 = p1;
+
+    System.out.println("   p1 = " + p1);
+    System.out.println("   p2 = " + p2);
+    System.out.println();
+
+    System.out.println("Nach dem Verschieben von p1 nach (4,5):");
+
+    p1.moveTo(4, 5);
+
+    System.out.println();
+    System.out.println("   p1 = (" + p1.x + "," + p1.y + ")");
+    System.out.println("   p2 = (" + p2.x + "," + p2.y + ")");
+    System.out.println();
+  }
+}
+
+// Verweise