finding the order of execution of the Jobs

Question

Suppose a job is represented by a single character. Maybe a job “a” must be completed before job “b”, then job “b” depends on “a”. Any job may depend on any number of other jobs. After registering jobs with their dependencies the class should compute the order of jobs for execution.

 

The interface is defined as:

 

interface OrderedJobs { void register(char job);

void register(char job, char dependentJob);

String[] sort();

}

 

For example, registering the following jobs:

register('c'); register('b', 'a'); register('c', 'b');

sort() should return this result: "abc".

 

The same job appeared in multiple registrations just occurs once in the result of sort(). Jobs with no dependency can occur in any order as long as they are executed before jobs which depend on them. Circular dependencies between jobs should be reported through an exception (at least in the method sort()).