[Chapter 30] 30.6 java.util.Enumeration (JDK 1.0)

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| Chapter 30 The java.util Package |

## 30.6 java.util.Enumeration (JDK 1.0)

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This interface defines the methods necessary to enumerate, or iterate through, a set of values, such as the set of values contained in a hashtable or binary tree. It is particularly useful for data structures, like hashtables, for which elements cannot simply be looked up by index, as they can in arrays. An `Enumeration` is usually not instantiated directly, but instead is created by the object that is to have its values enumerated. A number of classes, such as `Vector` and `Hashtable`, have methods that return `Enumeration` objects.

To use an `Enumeration` object, you use its two methods in a loop: `hasMoreElements()` returns `true` if there are more values to be enumerated, and can be used to determine whether a loop should continue. Within a loop, a call to `nextElement()` returns a value from the enumeration. An `Enumeration` makes no guarantees about the order in which the values are returned. The values in an `Enumeration` may be iterated through only once--there is no way to reset it to the beginning.

    public abstract interface Enumeration {
        // Public Instance Methods
                public abstract boolean hasMoreElements();
                public abstract Object nextElement();
    }

### Implemented By:

StringTokenizer

### Passed To:

SequenceInputStream()

### Returned By:

AppletContext.getApplets(), Dictionary.elements(), Dictionary.keys(), FeatureDescriptor.attributeNames(), Hashtable.elements(), Hashtable.keys(), ListResourceBundle.getKeys(), MenuBar.shortcuts(), Properties.propertyNames(), PropertyResourceBundle.getKeys(), ResourceBundle.getKeys(), Vector.elements(), ZipFile.entries()

java.util.EmptyStackException (JDK 1.0) |  | java.util.EventListener (JDK 1.1)