# Routing via Java API

To use the following examples you need to specify the dependency in
your [Maven config](/README.md#maven) correctly.

To do routing in your Java code you'll need just a few lines of code.

See [this code example](../../example/src/main/java/com/graphhopper/example/RoutingExample.java)
on how to do that where also code examples for the next sections are
included.

## Speed mode vs. Hybrid mode vs. Flexible mode

GraphHopper offers three different choices of algorithms for routing: The speed mode (which implements Contraction
Hierarchies (CH) and is by far the fastest), the hybrid mode (which uses Landmarks (LM) and is still fast, but also supports
some features CH does not support) and the flexible mode (Dijkstra or A*) which does not require calculating index data
and offers full flexibility and is comparable slow especially for longer routes.

See the [profiles](./profiles.md) for an explanation how to configure the different routing modes. At query time you
can disable speed mode using `ch.disable=true`. In this case either hybrid mode (if there is an LM preparation for the
chosen profile) or flexible mode will be used. To use flexible mode in the presence of an LM preparation you need to 
also set `lm.disable=true`.

To calculate a route you have to pick one vehicle and optionally an algorithm like
`bidirectional_astar`, see the test speedModeVersusHybridMode.

## Heading

The flexible and hybrid modes allow adding a desired heading (north based azimuth between 0 and 360 degree)
to any point. Adding a heading makes it more likely that a route starts towards the provided direction, because
roads going into other directions are penalized. See [heading](./heading.md) for an example and more information.

## Alternative Routes

For all modes you can calculate alternative routes. Note, that the algorithm
for CH is different to the algorithm used for LM or flexible mode. In all
caases this setting will affect the speed of your routing requests. See
the test headingAndAlternativeRoute and the Parameters class for further hints.

## Java client (client-hc)
 
If you want to calculate routes using the [GraphHopper Directions API](https://www.graphhopper.com/products/) or 
a self hosted instance of GraphHopper, you can use the [Java and Android client-hc](https://github.com/graphhopper/graphhopper/tree/master/client-hc):


```java
GraphHopperAPI gh = new GraphHopperWeb();
gh.load("http://your-graphhopper-service.com");

// or for the GraphHopper Directions API https://graphhopper.com/#directions-api
// gh.load("https://graphhopper.com/api/1/route");

GHResponse rsp = gh.route(new GHRequest(...));
```

There are also clients for [Java Script](https://github.com/graphhopper/directions-api-js-client) and [other languages](https://github.com/graphhopper/directions-api-clients)).