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6889858: Add nonNull methods to java.util.Objects

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Reviewed-by: darcy
This commit is contained in:
Joshua Bloch 2009-10-19 16:31:48 -07:00 committed by Joe Darcy
parent 302bb54494
commit c225292004
2 changed files with 96 additions and 0 deletions
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46
jdk/src/share/classes/java/util/Objects.java
View File

@ -107,4 +107,50 @@ public class Objects {
public static <T> int compare(T a, T b, Comparator<? super T> c) {
return (a == b) ? 0 : c.compare(a, b);
}
/**
* Checks that the specified object reference is not {@code null}. This
* method is designed primarily for doing parameter validation in methods
* and constructors, as demonstrated below:
* <blockquote><pre>
* public Foo(Bar bar) {
* this.bar = Objects.nonNull(bar);
* }
* </pre></blockquote>
*
* @param obj the object reference to check for nullity
* @param <T> the type of the reference
* @return {@code obj} if not {@code null}
* @throws NullPointerException if {@code obj} is {@code null}
*/
public static <T> T nonNull(T obj) {
if (obj == null)
throw new NullPointerException();
return obj;
}
/**
* Checks that the specified object reference is not {@code null} and
* throws a customized {@link NullPointerException} if it is. This method
* is designed primarily for doing parameter validation in methods and
* constructors with multiple parameters, as demonstrated below:
* <blockquote><pre>
* public Foo(Bar bar, Baz baz) {
* this.bar = Objects.nonNull(bar, "bar must not be null");
* this.baz = Objects.nonNull(baz, "baz must not be null");
* }
* </pre></blockquote>
*
* @param obj the object reference to check for nullity
* @param message detail message to be used in the event that a {@code
* NullPointerException} is thrown
* @param <T> the type of the reference
* @return {@code obj} if not {@code null}
* @throws NullPointerException if {@code obj} is {@code null}
*/
public static <T> T nonNull(T obj, String message) {
if (obj == null)
throw new NullPointerException(message);
return obj;
}
}

50
jdk/test/java/util/Objects/BasicObjectsTest.java
View File

@ -37,6 +37,7 @@ public class BasicObjectsTest {
errors += testHashCode();
errors += testToString();
errors += testCompare();
errors += testNonNull();
if (errors > 0 )
throw new RuntimeException();
}
@ -102,4 +103,53 @@ public class BasicObjectsTest {
}
return errors;
}
private static int testNonNull() {
int errors = 0;
String s;
// Test 1-arg variant
try {
s = Objects.nonNull("pants");
if (s != "pants") {
System.err.printf("1-arg non-null failed to return its arg");
errors++;
}
} catch (NullPointerException e) {
System.err.printf("1-arg nonNull threw unexpected NPE");
errors++;
}
try {
s = Objects.nonNull(null);
System.err.printf("1-arg nonNull failed to throw NPE");
errors++;
} catch (NullPointerException e) {
// Expected
}
// Test 2-arg variant
try {
s = Objects.nonNull("pants", "trousers");
if (s != "pants") {
System.err.printf("2-arg nonNull failed to return its arg");
errors++;
}
} catch (NullPointerException e) {
System.err.printf("2-arg nonNull threw unexpected NPE");
errors++;
}
try {
s = Objects.nonNull(null, "pantaloons");
System.err.printf("2-arg nonNull failed to throw NPE");
errors++;
} catch (NullPointerException e) {
if (e.getMessage() != "pantaloons") {
System.err.printf("2-arg nonNull threw NPE w/ bad detail msg");
errors++;
}
}
return errors;
}
}