Atomicity

Motivation

Many race conditions can be prevented by proper encapsulation avoiding check-then-write and read-write-modify patterns.

Background

Concurrency Tutorial

Synchronized Methods

Intrinsic Locks

Code To Investigate

class:	CheckThenActCourse.java	DEMO:
methods:	isSpaceRemaining add drop
package:	atomicity.course.studio
source folder:	src//java

public class CheckThenActCourse {
	private final Collection<Student> students;
	private final int limit;

	public CheckThenActCourse(int limit, Supplier<Collection<Student>> collectionSupplier) {
		this.students = collectionSupplier.get();
		this.limit = limit;
	}

	public int getLimit() {
		return this.limit;
	}

	public boolean isSpaceRemaining() {
		synchronized (this.students) {
			return this.students.size() < this.limit;
		}
	}

	public void add(Student student) {
		synchronized (this.students) {
			this.students.add(student);
		}
	}

	public boolean drop(Student student) {
		synchronized (this.students) {
			return this.students.remove(student);
		}
	}
}

Code To Implement

class:	Course.java
methods:	addIfSpace drop
package:	atomicity.course.studio
source folder:	student/src/main/java

method: public boolean addIfSpace(Student student) (sequential implementation only)

method: public boolean drop(Student student) (sequential implementation only)

Testing Your Solution

Correctness

class:	AtomicityTestSuite.java
package:	atomicity
source folder:	testing/src/test/java