Add Pair.toString(String)

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1091156 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -17,6 +17,7 @@
 package org.apache.commons.lang3;
 
 import java.io.Serializable;
+import java.util.Formatter;
 import java.util.Map;
 
 import org.apache.commons.lang3.builder.CompareToBuilder;
@@ -163,4 +164,12 @@ public abstract class Pair<L, R> implements Map.Entry<L, R>, Comparable<Pair<L,
         return builder.toString();
     }
 
+    /**
+     * Returns a String representation in the given format.
+     * @param format a {@link Formatter} String.
+     * @return a string for this object
+     */
+    public String toString(String format) {
+        return String.format(format, getClass().getSimpleName(), getLeftElement(), getRightElement());
+    }
 }

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

@@ -96,4 +96,15 @@ public class PairTest {
         assertEquals("(Key,Value)", pair.toString());
     }
 
+    @Test
+    public void testToStringFormat() throws Exception {
+        Pair<String, String> pair = Pair.of("Key", "Value");
+        assertEquals("ImmutablePair", pair.toString("%1$s"));
+        assertEquals("Key", pair.toString("%2$s"));
+        assertEquals("Value", pair.toString("%3$s"));
+        assertEquals("Key: Value", pair.toString("%2$s: %3$s"));
+        pair = Pair.of(null, null);
+        assertEquals("null: null", pair.toString("%2$s: %3$s"));
+    }
+
 }