diff options
Diffstat (limited to 'libjava/java/util/Stack.java')
| -rw-r--r-- | libjava/java/util/Stack.java | 58 |
1 files changed, 33 insertions, 25 deletions
diff --git a/libjava/java/util/Stack.java b/libjava/java/util/Stack.java index 8647fa4..a7b3f5d4 100644 --- a/libjava/java/util/Stack.java +++ b/libjava/java/util/Stack.java @@ -32,24 +32,30 @@ package java.util; * "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 - */ /** * Stack provides a Last In First Out (LIFO) data type, commonly known - * as a Stack. - * - * Stack itself extends Vector and provides the additional methods - * for stack manipulation (push, pop, peek). + * as a Stack. Stack itself extends Vector and provides the additional + * methods for stack manipulation (push, pop, peek). You can also seek for + * the 1-based position of an element on the stack. * * @author Warren Levy <warrenl@cygnus.com> - * @date August 20, 1998. + * @author Eric Blake <ebb9@email.byu.edu> + * @see List + * @see AbstractList + * @see LinkedList + * @since 1.0 + * @status updated to 1.4 */ public class Stack extends Vector { - // Could use Vector methods internally for the following methods + // We 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). + /** + * Compatible with JDK 1.0+. + */ private static final long serialVersionUID = 1224463164541339165L; /** @@ -57,16 +63,15 @@ public class Stack extends Vector */ public Stack() { - super(); } /** * Pushes an Object onto the top of the stack. This method is effectively - * the same as addElement(item) + * the same as addElement(item). * * @param item the Object to push onto the stack - * @returns the Object pushed onto the stack - * @see java.util.Vector#addElement(java.util.Object) + * @return the Object pushed onto the stack + * @see Vector#addElement(Object) */ public Object push(Object item) { @@ -80,26 +85,29 @@ public class Stack extends Vector /** * Pops an item from the stack and returns it. The item popped is - * removed from the Stack + * removed from the Stack. * - * @returns the Object popped from the stack + * @return the Object popped from the stack + * @throws EmptyStackException if the stack is empty */ public synchronized Object pop() { if (elementCount == 0) throw new EmptyStackException(); + modCount++; Object obj = elementData[--elementCount]; - // Set topmost element to null to assist the gc in cleanup + // Set topmost element to null to assist the gc in cleanup. elementData[elementCount] = null; return obj; } /** - * Returns the top Object on the stack without removing it + * Returns the top Object on the stack without removing it. * - * @returns the top Object on the stack + * @return the top Object on the stack + * @throws EmptyStackException if the stack is empty */ public synchronized Object peek() { @@ -110,11 +118,11 @@ public class Stack extends Vector } /** - * Tests if the stack is empty + * Tests if the stack is empty. * - * @returns true if the stack contains no items, false otherwise + * @return true if the stack contains no items, false otherwise */ - public boolean empty() + public synchronized boolean empty() { return elementCount == 0; } @@ -122,18 +130,18 @@ public class Stack extends Vector /** * Returns the position of an Object on the stack, with the top * most Object being at position 1, and each Object deeper in the - * stack at depth + 1 + * stack at depth + 1. * * @param o The object to search for - * @returns The 1 based depth of the Object, or -1 if the Object - * is not on the stack. + * @return The 1 based depth of the Object, or -1 if the Object + * is not on the stack */ public synchronized int search(Object o) { - for (int i = elementCount-1; i >=0; --i) - if (elementData[i].equals(o)) + int i = elementCount; + while (--i >= 0) + if (equals(o, elementData[i])) return elementCount - i; - return -1; } } |