ContactUpdateHandler (dyn4j 4.0.0 API)

```
public interface ContactUpdateHandler
```
This interface defines the mechanism to report begin, persist, and end events and the method of mixing the friction and restitution coefficients.

Since:

4.0.0

Version:

4.0.0

Author:

William Bittle

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`void`	`begin(Contact contact)`	Called when the given contact is a new contact.
`void`	`end(Contact contact)`	Called when the given contact was ended.
`double`	`getFriction(BodyFixture fixture1, BodyFixture fixture2)`	Returns the coefficient of friction given the two `BodyFixture`s in contact.
`double`	`getRestitution(BodyFixture fixture1, BodyFixture fixture2)`	Returns the coefficient of restitution given the two `BodyFixture`s in contact.
`void`	`persist(Contact oldContact, Contact newContact)`	Called when the given contact was persisted.

- Method Detail
  - getFriction
```
double getFriction(BodyFixture fixture1,
                   BodyFixture fixture2)
```
    Returns the coefficient of friction given the two BodyFixtures in contact.
    
    Parameters:
    
    fixture1 - the first fixture
    
    fixture2 - the second fixture
    
    Returns:
    
    double
  - getRestitution
```
double getRestitution(BodyFixture fixture1,
                      BodyFixture fixture2)
```
    Returns the coefficient of restitution given the two BodyFixtures in contact.
    
    Parameters:
    
    fixture1 - the first fixture
    
    fixture2 - the second fixture
    
    Returns:
    
    double
  - begin
```
void begin(Contact contact)
```
    Called when the given contact is a new contact.
    A new contact is a contact that either didn't exist before or one that could not be warm started.
    
    Parameters:
    
    contact - the new contact
  - persist
```
void persist(Contact oldContact,
             Contact newContact)
```
    Called when the given contact was persisted.
    A persisted contact is a contact that existed before and the new contact just updates the old.
    
    Parameters:
    
    oldContact - the old contact
    
    newContact - the new contact
  - end
```
void end(Contact contact)
```
    Called when the given contact was ended.
    An ended contact is a contact that no longer exists.
    
    Parameters:
    
    contact - the ended contact