
This page provides an overview of the classes comprising the Java binding for e4Graph.
The Java API consists of classes representing the main entities of e4Graph: Storage, Node, and Vertex. Each of these classes provides methods for invoking the various operations provided by the underlying e4Graph classes. The classes StorageIterator, VertexIterator and ParentIterator allow a client program to iterate over all open storages, over vertices in a node and over parent nodes of a node, respectively.
Here's a small example similar to the C++ example on the introduction page.
Storage s = new Storage("John's grocery store", Storage.METAKIT);
Node root;
Node items;
Node sugar;
double price_per_pound;
int pound_in_store;
try {
root = s.getRoot();
items = root.getNode("on hand items");
sugar = items.getNode("sugar");
pounds_in_store = sugar.getInt("pounds in store");
price_per_pound = sugar.getDouble("price per pound");
System.out.println("John's store has " + pounds_in_store +
" pounds of sugar at " + price_per_pound +
" per pound");
sugar.setDouble("price per pound", price_per_pound+0.05);
} catch (...) {
...
}
All of this corresponds exactly to the C++ example, except for error
handling. In Java, errors are propagated by throwing exceptions.