001 /* Copyright (c) 2000-2010 hamcrest.org
002 */
003 package org.hamcrest.core;
004
005 import static org.hamcrest.core.IsNot.not;
006 import org.hamcrest.Description;
007 import org.hamcrest.Matcher;
008 import org.hamcrest.Factory;
009 import org.hamcrest.BaseMatcher;
010
011 /**
012 * Is the value null?
013 */
014 public class IsNull<T> extends BaseMatcher<T> {
015 @Override
016 public boolean matches(Object o) {
017 return o == null;
018 }
019
020 @Override
021 public void describeTo(Description description) {
022 description.appendText("null");
023 }
024
025 /**
026 * Creates a matcher that matches if examined object is <code>null</code>.
027 * <p/>
028 * For example:
029 * <pre>assertThat(cheese, is(nullValue())</pre>
030 *
031 */
032 @Factory
033 public static Matcher<Object> nullValue() {
034 return new IsNull<Object>();
035 }
036
037 /**
038 * A shortcut to the frequently used <code>not(nullValue())</code>.
039 * <p/>
040 * For example:
041 * <pre>assertThat(cheese, is(notNullValue()))</pre>
042 * instead of:
043 * <pre>assertThat(cheese, is(not(nullValue())))</pre>
044 *
045 */
046 @Factory
047 public static Matcher<Object> notNullValue() {
048 return not(nullValue());
049 }
050
051 /**
052 * Creates a matcher that matches if examined object is <code>null</code>. Accepts a
053 * single dummy argument to facilitate type inference.
054 * <p/>
055 * For example:
056 * <pre>assertThat(cheese, is(nullValue(Cheese.class))</pre>
057 *
058 * @param type
059 * dummy parameter used to infer the generic type of the returned matcher
060 */
061 @Factory
062 public static <T> Matcher<T> nullValue(Class<T> type) {
063 return new IsNull<T>();
064 }
065
066 /**
067 * A shortcut to the frequently used <code>not(nullValue(X.class)). Accepts a
068 * single dummy argument to facilitate type inference.</code>.
069 * <p/>
070 * For example:
071 * <pre>assertThat(cheese, is(notNullValue(X.class)))</pre>
072 * instead of:
073 * <pre>assertThat(cheese, is(not(nullValue(X.class))))</pre>
074 *
075 * @param type
076 * dummy parameter used to infer the generic type of the returned matcher
077 *
078 */
079 @Factory
080 public static <T> Matcher<T> notNullValue(Class<T> type) {
081 return not(nullValue(type));
082 }
083 }
084