[LANG-1393] Add API SystemUtils.String getEnvironmentVariable(final

String name, final String defaultValue).

src/changes/changes.xml

@@ -59,6 +59,7 @@ The <action> type attribute can be add,update,fix,remove.
     <action issue="LANG-1372" type="add" dev="pschumacher" due-to="Sérgio Ozaki">Add ToStringSummary annotation</action>
     <action issue="LANG-1356" type="add" dev="pschumacher" due-to="Yathos UG">Add bypass option for classes to recursive and reflective EqualsBuilder</action>
     <action issue="LANG-1391" type="add" dev="ggregory" due-to="Sauro Matulli, Oleg Chubaryov">Improve Javadoc for StringUtils.isAnyEmpty(null)</action>   
+    <action issue="LANG-1393" type="add" dev="ggregory" due-to="Gary Gregory">Add API SystemUtils.String getEnvironmentVariable(final String name, final String defaultValue)</action>   
   </release>
 
   <release version="3.7" date="2017-11-04" description="New features and bug fixes. Requires Java 7, supports Java 8, 9, 10.">

src/main/java/org/apache/commons/lang3/SystemUtils.java

@@ -1605,6 +1605,33 @@ private static String getSystemProperty(final String property) {
         }
     }
 
+    /**
+     * <p>
+     * Gets an environment variable, defaulting to {@code defaultValue} if the variable cannot be read.
+     * </p>
+     * <p>
+     * If a {@code SecurityException} is caught, the return value is {@code defaultValue} and a message is written to
+     * {@code System.err}.
+     * </p>
+     *
+     * @param name
+     *            the environment variable name
+     * @param defaultValue
+     *            the default value
+     * @return the environment variable value or {@code defaultValue} if a security problem occurs
+     * @since 3.7
+     */
+    public static String getEnvironmentVariable(final String name, final String defaultValue) {
+        try {
+            final String value = System.getenv(name);
+            return value == null ? defaultValue : value;
+        } catch (final SecurityException ex) {
+            // we are not allowed to look at this property
+            System.err.println("Caught a SecurityException reading the environment variable '" + name + "'.");
+            return defaultValue;
+        }
+    }
+
     /**
      * <p>
      * Gets the user directory as a {@code File}.

src/test/java/org/apache/commons/lang3/SystemUtilsTest.java

@@ -40,6 +40,7 @@
 import java.lang.reflect.Modifier;
 import java.util.Locale;
 
+import org.junit.Assert;
 import org.junit.Test;
 
 /**
@@ -59,6 +60,23 @@ public void testConstructor() {
         assertFalse(Modifier.isFinal(SystemUtils.class.getModifiers()));
     }
 
+    @Test
+    public void testGetEnvironmentVariableAbsent() {
+        final String name = "THIS_ENV_VAR_SHOULD_NOT_EXIST_FOR_THIS_TEST_TO_PASS";
+        final String expected = System.getenv(name);
+        Assert.assertNull(expected);
+        final String value = SystemUtils.getEnvironmentVariable(name, "DEFAULT");
+        assertEquals("DEFAULT", value);
+    }
+
+    @Test
+    public void testGetEnvironmentVariablePresent() {
+        final String name = "PATH";
+        final String expected = System.getenv(name);
+        final String value = SystemUtils.getEnvironmentVariable(name, null);
+        assertEquals(expected, value);
+    }
+
     @Test
     public void testGetHostName() {
         final String hostName = SystemUtils.getHostName();