Merge pull request matyb#54 from godfreyduke/master

matyb · matyb · commit cd73a1b68de5 · 2015-10-18T20:10:19.000-04:00
Add koans for argument validation using exceptions and Object.requireNotNull.
diff --git a/koans/app/config/PathToEnlightenment.xml b/koans/app/config/PathToEnlightenment.xml
@@ -43,6 +43,7 @@
 		<suite class="AboutStringsInSwitch"/>
 		<suite class="AboutDiamondOperator"/>
 		<suite class="AboutTryWithResources"/>
+                <suite class="AboutRequireNotNull"/>
 	</package>
 	<package pkg="java8" name="Java 8">
 		<suite class="AboutDefaultMethods"/>
diff --git a/koans/src/beginner/AboutExceptions.java b/koans/src/beginner/AboutExceptions.java
@@ -124,4 +124,38 @@ public void catchOrder() {
 		}
 		assertEquals(s, __);
 	}	
+
+	@Koan
+	public void failArgumentValidationWithAnIllegalArgumentException(){
+		// This koan demonstrates the use of exceptions in argument validation
+		String s = "";
+		try {
+			s += validateUsingIllegalArgumentException(null);
+		} catch (IllegalArgumentException ex) {
+			s = "caught an IllegalArgumentException";
+		}
+		assertEquals(s, __);
+	}
+	
+	@Koan
+	public void passArgumentValidationWithAnIllegalArgumentException(){
+		// This koan demonstrates the use of exceptions in argument validation
+		String s = "";
+		try {
+			s += validateUsingIllegalArgumentException("valid");
+		} catch (IllegalArgumentException ex) {
+			s = "caught an IllegalArgumentException";
+		}
+		assertEquals(s, __);
+	}
+
+	private int validateUsingIllegalArgumentException(String str) {
+		// This is effective and both the evaluation and the error message
+		// can be tailored which can be particularly handy if you're guarding
+		// against more than null values
+		if (null == str) {
+			throw new IllegalArgumentException("str should not be null");	
+		}
+		return str.length();
+	}
 }
diff --git a/koans/src/java7/AboutRequireNotNull.java b/koans/src/java7/AboutRequireNotNull.java
@@ -0,0 +1,47 @@
+package java7;
+
+import static com.sandwich.koan.constant.KoanConstants.__;
+import static com.sandwich.util.Assert.assertEquals;
+import static com.sandwich.util.Assert.fail;
+
+import java.util.Objects;
+
+import com.sandwich.koan.Koan;
+
+public class AboutRequireNotNull {
+	
+	@Koan
+	public void failArgumentValidationWithRequireNotNull(){
+		// This koan demonstrates the use of Objects.requireNotNull
+		// in place of traditional argument validation using exceptions
+		String s = "";
+		try {
+			s += validateUsingRequireNotNull(null);
+		} catch (NullPointerException ex) {
+			s = "caught a NullPointerException";
+		}
+		assertEquals(s, __);
+	}
+	
+	@Koan
+	public void passArgumentValidationWithRequireNotNull(){
+		// This koan demonstrates the use of Objects.requireNotNull
+		// in place of traditional argument validation using exceptions		
+		String s = "";
+		try {
+			s += validateUsingRequireNotNull("valid");
+		} catch (NullPointerException ex) {
+			s = "caught a NullPointerException";
+		}
+		assertEquals(s, __);
+	}
+	
+	private int validateUsingRequireNotNull(String str) {
+		// If you're only concerned with null values requireNotNull
+		// is concise and the point of the NullPointerException it
+		// throws is clear, though you can optionally provide a
+		// description as well
+		return Objects.requireNonNull(str).length();
+	}
+		
+}
