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Add Suppliers.nul()

This commit is contained in:
Gary Gregory 2023-10-16 09:16:22 -04:00
parent 13839dae6e
commit 6c61b0916e
6 changed files with 45 additions and 17 deletions
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1
src/changes/changes.xml
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@ -73,6 +73,7 @@ The <action> type attribute can be add,update,fix,remove.
<action type="add" dev="ggregory" due-to="Benjamin Confino, Gary Gregory">Add ConcurrentInitializer#isInitialized() #1120.</action>
<action type="add" dev="ggregory" due-to="Gary Gregory">Add Streams.failableStream(T...).</action>
<action type="add" dev="ggregory" due-to="Gary Gregory">Add FailableSupplier.nul().</action>
<action type="add" dev="ggregory" due-to="Gary Gregory">Add Suppliers.nul().</action>
<!-- UPDATE -->
<action type="update" dev="ggregory" due-to="Gary Gregory">Bump commons-parent from 58 to 64.</action>
<action type="update" dev="ggregory" due-to="Gary Gregory">Bump org.easymock:easymock from 5.1.0 to 5.2.0 #1104.</action>

6
src/main/java/org/apache/commons/lang3/SystemProperties.java
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@ -22,6 +22,8 @@ import java.util.function.IntSupplier;
import java.util.function.LongSupplier;
import java.util.function.Supplier;
import org.apache.commons.lang3.function.Suppliers;
/**
* Accesses current system property names and values.
*
@ -29,8 +31,6 @@ import java.util.function.Supplier;
*/
public final class SystemProperties {
private static final Supplier<String> NULL_SUPPLIER = () -> null;
/**
* The System property name {@value}.
*/
@ -752,7 +752,7 @@ public final class SystemProperties {
* @return the system property value or {@code null} if a security problem occurs
*/
public static String getProperty(final String property) {
return getProperty(property, NULL_SUPPLIER);
return getProperty(property, Suppliers.nul());
}
/**

24
src/main/java/org/apache/commons/lang3/function/Suppliers.java
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@ -26,6 +26,30 @@ import java.util.function.Supplier;
*/
public class Suppliers {
/**
* Returns the singleton supplier that always returns null.
* <p>
* This supplier never throws an exception.
* </p>
*/
@SuppressWarnings("rawtypes")
private static Supplier NUL = () -> null;
/**
* Returns the singleton supplier that always returns null.
* <p>
* This supplier never throws an exception.
* </p>
*
* @param <T> Supplied type.
* @return The NUL singleton.
* @since 3.14.0
*/
@SuppressWarnings("unchecked")
public static <T> Supplier<T> nul() {
return NUL;
}
/**
* Null-safe call to {@link Supplier#get()}.
*

25
src/test/java/org/apache/commons/lang3/ObjectUtilsTest.java
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@ -47,6 +47,7 @@ import java.util.Set;
import java.util.function.Supplier;
import org.apache.commons.lang3.exception.CloneFailedException;
import org.apache.commons.lang3.function.Suppliers;
import org.apache.commons.lang3.mutable.MutableInt;
import org.apache.commons.lang3.mutable.MutableObject;
import org.apache.commons.lang3.text.StrBuilder;
@ -479,14 +480,14 @@ public class ObjectUtilsTest extends AbstractLangTest {
@Test
public void testGetFirstNonNull() {
// first non-null
assertEquals("", ObjectUtils.getFirstNonNull(() -> null, () -> ""));
assertEquals("", ObjectUtils.getFirstNonNull(Suppliers.nul(), () -> ""));
// first encountered value is used
assertEquals("1", ObjectUtils.getFirstNonNull(() -> null, () -> "1", () -> "2", () -> null));
assertEquals("123", ObjectUtils.getFirstNonNull(() -> "123", () -> null, () -> "456"));
assertEquals("1", ObjectUtils.getFirstNonNull(Suppliers.nul(), () -> "1", () -> "2", Suppliers.nul()));
assertEquals("123", ObjectUtils.getFirstNonNull(() -> "123", Suppliers.nul(), () -> "456"));
// don't evaluate suppliers after first value is found
assertEquals("123", ObjectUtils.getFirstNonNull(() -> null, () -> "123", () -> fail("Supplier after first non-null value should not be evaluated")));
assertEquals("123", ObjectUtils.getFirstNonNull(Suppliers.nul(), () -> "123", () -> fail("Supplier after first non-null value should not be evaluated")));
// supplier returning null and null supplier both result in null
assertNull(ObjectUtils.getFirstNonNull(null, () -> null));
assertNull(ObjectUtils.getFirstNonNull(null, Suppliers.nul()));
// Explicitly pass in an empty array of Object type to ensure compiler doesn't complain of unchecked generic array creation
assertNull(ObjectUtils.getFirstNonNull());
// supplier is null
@ -494,8 +495,8 @@ public class ObjectUtilsTest extends AbstractLangTest {
// varargs array itself is null
assertNull(ObjectUtils.getFirstNonNull((Supplier<Object>[]) null));
// test different types
assertEquals(1, ObjectUtils.getFirstNonNull(() -> null, () -> 1));
assertEquals(Boolean.TRUE, ObjectUtils.getFirstNonNull(() -> null, () -> Boolean.TRUE));
assertEquals(1, ObjectUtils.getFirstNonNull(Suppliers.nul(), () -> 1));
assertEquals(Boolean.TRUE, ObjectUtils.getFirstNonNull(Suppliers.nul(), () -> Boolean.TRUE));
}
@Test
@ -849,7 +850,7 @@ public class ObjectUtilsTest extends AbstractLangTest {
@Test
public void testToString_String_Supplier() {
assertNull(ObjectUtils.toString(null, (Supplier<String>) null));
assertNull(ObjectUtils.toString(null, () -> null));
assertNull(ObjectUtils.toString(null, Suppliers.nul()));
// Pretend computing BAR is expensive.
assertEquals(BAR, ObjectUtils.toString(null, () -> BAR));
assertEquals(Boolean.TRUE.toString(), ObjectUtils.toString(Boolean.TRUE, () -> BAR));
@ -858,12 +859,12 @@ public class ObjectUtilsTest extends AbstractLangTest {
@Test
public void testToString_Supplier_Supplier() {
assertNull(ObjectUtils.toString(NULL_SUPPLIER, (Supplier<String>) null));
assertNull(ObjectUtils.toString(() -> null, (Supplier<String>) null));
assertNull(ObjectUtils.toString(NULL_SUPPLIER, () -> null));
assertNull(ObjectUtils.toString(() -> null, () -> null));
assertNull(ObjectUtils.toString(Suppliers.nul(), (Supplier<String>) null));
assertNull(ObjectUtils.toString(NULL_SUPPLIER, Suppliers.nul()));
assertNull(ObjectUtils.toString(Suppliers.nul(), Suppliers.nul()));
// Pretend computing BAR is expensive.
assertEquals(BAR, ObjectUtils.toString(NULL_SUPPLIER, () -> BAR));
assertEquals(BAR, ObjectUtils.toString(() -> null, () -> BAR));
assertEquals(BAR, ObjectUtils.toString(Suppliers.nul(), () -> BAR));
assertEquals(Boolean.TRUE.toString(), ObjectUtils.toString(() -> Boolean.TRUE, () -> BAR));
}

5
src/test/java/org/apache/commons/lang3/StringUtilsTest.java
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@ -42,6 +42,7 @@ import java.util.Objects;
import java.util.function.Supplier;
import java.util.regex.PatternSyntaxException;
import org.apache.commons.lang3.function.Suppliers;
import org.apache.commons.lang3.mutable.MutableInt;
import org.apache.commons.lang3.text.WordUtils;
import org.junit.jupiter.api.Disabled;
@ -682,7 +683,7 @@ public class StringUtilsTest extends AbstractLangTest {
assertEquals("NULL", StringUtils.getIfBlank("", () -> "NULL"));
assertEquals("NULL", StringUtils.getIfBlank(" ", () -> "NULL"));
assertEquals("abc", StringUtils.getIfBlank("abc", () -> "NULL"));
assertNull(StringUtils.getIfBlank("", () -> null));
assertNull(StringUtils.getIfBlank("", Suppliers.nul()));
assertNull(StringUtils.defaultIfBlank("", (String) null));
// Tests compatibility for the API return type
final String s = StringUtils.getIfBlank("abc", () -> "NULL");
@ -750,7 +751,7 @@ public class StringUtilsTest extends AbstractLangTest {
assertEquals("NULL", StringUtils.getIfEmpty((String) null, () -> "NULL"));
assertEquals("NULL", StringUtils.getIfEmpty("", () -> "NULL"));
assertEquals("abc", StringUtils.getIfEmpty("abc", () -> "NULL"));
assertNull(StringUtils.getIfEmpty("", () -> null));
assertNull(StringUtils.getIfEmpty("", Suppliers.nul()));
assertNull(StringUtils.defaultIfEmpty("", (String) null));
// Tests compatibility for the API return type
final String s = StringUtils.getIfEmpty("abc", () -> "NULL");

1
src/test/java/org/apache/commons/lang3/function/SuppliersTest.java
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@ -37,6 +37,7 @@ public class SuppliersTest extends AbstractLangTest {
public void testGet() {
assertNull(Suppliers.get(null));
assertNull(Suppliers.get(() -> null));
assertNull(Suppliers.get(Suppliers.nul()));
assertEquals("foo", Suppliers.get(() -> "foo"));
}
}