Startpunkten

Java_Database/Element.java

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+/**
+*  This is a class containing functios 
+*  for the Elements in the list.
+*
+*
+*       @author Christian Ohlsson, Karlstad university 1999
+*       @version 1.0.0
+*/
+public class Element { 
+  Element suc; 
+ 
+/**
+* This is just the constructor.
+*/   
+  public Element() { suc = null; } 
+
+/**   
+*  Returns the current Element in the list
+*/
+  public Element suc() { return suc; } 
+
+/**
+*  This function inserts a new Element
+*  at the end of the List. 
+*  It first checks out if the List is empty, 
+*  i.e the first Element is null, and then
+*  the first Element is this Element.
+*  Otherwise, it inserts the new Element
+*  at the end of the List. 
+*/
+  public void into(List theList) { 
+    if (theList.first==null) 
+      theList.first = theList.last = this; 
+    else { 
+      theList.last.suc = this; 
+      theList.last = this; 
+    } 
+    suc = null; 
+  } 
+     
+/**
+*  This function inserts a new Element at
+*  the beginning of the list. 
+*  It first checks out if the List is empty, 
+*  i.e the first Element is null, and then
+*  the first Element is this Element.
+*  Otherwise, the Element that were in the
+*  beginning, now is in second place and
+*  the new Element is in front of the List.
+*/
+  public void intoAsFirst(List theList) { 
+    if (theList.first==null) { 
+      theList.first = theList.last = this; 
+      suc = null; 
+    } 
+    else { 
+      suc = theList.first; 
+      theList.first = this; 
+    } 
+  } 
+    
+/**
+*  This function deletes an Element in
+*  the List by traversing through the
+*  List until it gets to the Element
+*  that should be deleted. 
+*/
+  public void out(List theList) { 
+    Element prev = null; 
+    Element e = theList.first; 
+    while (e!=null && e!=this) { 
+      prev = e; 
+      e = e.suc; 
+    } 
+    if (e!=null) { 
+      if (theList.last==this) 
+        theList.last = prev; 
+      if (theList.first==this) 
+	  theList.first = suc; 
+      else 
+        prev.suc = suc; 
+      suc = null; 
+    } 
+  }
+}
+