implement circular-buffer & make requested fixes

config.json

@@ -469,6 +469,15 @@
       ]
     },
     {
+      "slug": "circular-buffer",
+      "difficulty": 8,
+      "topics": [
+        "Queues",
+        "Classes",
+        "Exception handling"
+      ]
+    },
+    {
       "slug": "rectangles",
       "difficulty": 8,
       "topics": [

exercises/circular-buffer/build.gradle

@@ -0,0 +1,18 @@
+apply plugin: "java"
+apply plugin: "eclipse"
+apply plugin: "idea"
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    testCompile "junit:junit:4.12"
+}
+
+test {
+    testLogging {
+        exceptionFormat = 'full'
+        events = ["passed", "failed", "skipped"]
+    }
+}

exercises/circular-buffer/src/example/java/BufferIOException.java

@@ -0,0 +1,6 @@
+public class BufferIOException extends Exception {
+
+    BufferIOException(String message) {
+        super(message);
+    }
+}

exercises/circular-buffer/src/example/java/CircularBuffer.java

@@ -0,0 +1,41 @@
+import java.util.LinkedList;
+import java.util.Queue;
+
+public class CircularBuffer<T> {
+
+    private Queue<T> buffer;
+    private int capacity;
+
+    public CircularBuffer(int size) {
+        this.buffer = new LinkedList<>();
+        this.capacity = size;
+    }
+
+    public T read() throws BufferIOException {
+        if (this.buffer.size() == 0) {
+            throw new BufferIOException("Tried to read from empty buffer");
+        }
+
+        return this.buffer.remove();
+    }
+
+    public void write(T data) throws BufferIOException {
+        if (this.buffer.size() == this.capacity) {
+            throw new BufferIOException("Tried to write to full buffer");
+        }
+
+        this.buffer.add(data);
+    }
+    public void overwrite(T data) {
+        if (this.buffer.size() == this.capacity) {
+            this.buffer.remove();
+        }
+
+        this.buffer.add(data);
+    }
+
+    public void clear() {
+        this.buffer.clear();
+    }
+}
+

exercises/circular-buffer/src/main/java/BufferIOException.java

@@ -0,0 +1,6 @@
+public class BufferIOException extends Exception {
+
+    BufferIOException(String message) {
+        super(message);
+    }
+}

exercises/circular-buffer/src/test/java/CircularBufferTest.java

@@ -0,0 +1,162 @@
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Ignore;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+public class CircularBufferTest {
+
+    @Rule
+    public ExpectedException expectedException = ExpectedException.none();
+
+    @Test
+    public void readingFromEmptyBufferShouldThrowException() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(1);
+
+        expectedException.expect(BufferIOException.class);
+        expectedException.expectMessage("Tried to read from empty buffer");
+        buffer.read();
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void canReadItemJustWritten() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(1);
+
+        buffer.write(1);
+        assertEquals((int) buffer.read(), 1);
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void canReadItemOnlyOnce() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(1);
+
+        buffer.write(1);
+        assertEquals((int) buffer.read(), 1);
+
+        expectedException.expect(BufferIOException.class);
+        expectedException.expectMessage("Tried to read from empty buffer");
+        buffer.read();
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void readsItemsInOrderWritten() throws BufferIOException { 
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(2);
+
+        buffer.write(1);
+        buffer.write(2);
+        assertEquals((int) buffer.read(), 1);
+        assertEquals((int) buffer.read(), 2);
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void fullBufferCantBeWrittenTo() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(1);
+
+        buffer.write(1);
+        expectedException.expect(BufferIOException.class);
+        expectedException.expectMessage("Tried to write to full buffer");
+        buffer.write(2);
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void readFreesUpSpaceForWrite() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(1);
+
+        buffer.write(1);
+        assertEquals((int) buffer.read(), 1);
+        buffer.write(2);
+        assertEquals((int) buffer.read(), 2);
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void maintainsReadPositionAcrossWrites() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(3);
+
+        buffer.write(1);
+        buffer.write(2);
+        assertEquals((int) buffer.read(), 1);
+        buffer.write(3);
+        assertEquals((int) buffer.read(), 2);
+        assertEquals((int) buffer.read(), 3);
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void cantReadClearedItems() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(1);
+
+        buffer.write(1);
+        buffer.clear();
+        expectedException.expect(BufferIOException.class);
+        expectedException.expectMessage("Tried to read from empty buffer");
+        buffer.read();
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void clearFreesUpCapacity() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(1);
+
+        buffer.write(1);
+        buffer.clear();
+        buffer.write(2);
+        assertEquals((int) buffer.read(), 2);
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void clearDoesNothingOnEmptyBuffer() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(1);
+
+        buffer.clear();
+        buffer.write(1);
+        assertEquals((int) buffer.read(), 1);
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void overwriteActsLikeWriteOnNonFullBuffer() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(2);
+
+        buffer.write(1);
+        buffer.overwrite(2);
+        assertEquals((int) buffer.read(), 1);
+        assertEquals((int) buffer.read(), 2);
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void overwriteRemovesOldestElementOnFullBuffer() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(2);
+
+        buffer.write(1);
+        buffer.write(2);
+        buffer.overwrite(3);
+        assertEquals((int) buffer.read(), 2);
+        assertEquals((int) buffer.read(), 3);
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void overwriteDoesntRemoveAnAlreadyReadElement() throws BufferIOException {
+        CircularBuffer<Integer> buffer = new CircularBuffer<>(3);
+
+        buffer.write(1);
+        buffer.write(2);
+        buffer.write(3);
+        assertEquals((int) buffer.read(), 1);
+        buffer.write(4);
+        buffer.overwrite(5);
+        assertEquals((int) buffer.read(), 3);
+        assertEquals((int) buffer.read(), 4);
+        assertEquals((int) buffer.read(), 5);
+    }
+}
+

exercises/settings.gradle

@@ -14,6 +14,7 @@ include 'book-store'
 include 'bowling'
 include 'bracket-push'
 include 'change'
+include 'circular-buffer'
 include 'clock'
 include 'collatz-conjecture'
 include 'complex-numbers'