Initial revision

From-SVN: r26263

libjava/java/util/Stack.java

@@ -0,0 +1,74 @@
+/* Copyright (C) 1998, 1999  Cygnus Solutions
+
+   This file is part of libgcj.
+
+This software is copyrighted work licensed under the terms of the
+Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
+details.  */
+
+package java.util;
+
+/**
+ * @author Warren Levy <warrenl@cygnus.com>
+ * @date August 20, 1998.
+ */
+/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
+ * "The Java Language Specification", ISBN 0-201-63451-1
+ * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
+ * Status:  Believed complete and correct
+ */
+
+public class Stack extends Vector
+{
+  // Could use Vector methods internally for the following methods
+  // but have used Vector fields directly for efficiency (i.e. this
+  // often reduces out duplicate bounds checking).
+
+  public boolean empty()
+  {
+    return elementCount == 0;
+  }
+
+  public synchronized Object peek()
+  {
+    if (elementCount == 0)
+      throw new EmptyStackException();
+
+    return elementData[elementCount - 1];
+  }
+
+  public synchronized Object pop()
+  {
+    if (elementCount == 0)
+      throw new EmptyStackException();
+
+    Object obj = elementData[--elementCount];
+
+    // Set topmost element to null to assist the gc in cleanup
+    elementData[elementCount] = null;
+    return obj;
+  }
+
+  public Object push(Object obj)
+  {
+    // When growing the Stack, use the Vector routines in case more
+    // memory is needed.
+    // Note: spec indicates that this method *always* returns obj passed in!
+
+    addElement(obj);
+    return obj;
+  }
+
+  public synchronized int search(Object obj)
+  {
+    // Return the position of obj on the stack as measured from the top;
+    // i.e. the top element is 1, the next element down is 2, etc.
+    // If obj is not on the stack, return -1
+
+    for (int i = elementCount-1; i >=0; --i)
+      if (elementData[i].equals(obj))
+	return elementCount - i;
+
+    return -1;
+  }
+}