[extract-ip] extract ip (#17917)

Author: sk1418

core-java-modules/core-java-regex-3/src/test/java/com/baeldung/extractip/ExtractIpAddressUnitTest.java

@@ -0,0 +1,53 @@
+package com.baeldung.extractip;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.junit.jupiter.api.Test;
+
+public class ExtractIpAddressUnitTest {
+
+    private static final String INPUT1 = "No IP address here";
+    private static final List<String> EXPECTED1 = Collections.emptyList();
+
+    private static final String INPUT2 = "My local ip is 127.0.0.1";
+    private static final List<String> EXPECTED2 = List.of("127.0.0.1");
+
+    private static final String INPUT3 = "Another ip address is 192.168.42.42";
+    private static final List<String> EXPECTED3 = List.of("192.168.42.42");
+
+    private static final String INPUT4 = "Extract the valid part: 260.1.2.345";
+    private static final List<String> EXPECTED4 = List.of("60.1.2.34");
+
+    private static final String INPUT5 = "No valid ip address 260.42.342.345";
+    private static final List<String> EXPECTED5 = Collections.emptyList();
+
+    private static final String INPUT6 = "We have multiple ip addresses: 127.1.1.0, 192.168.42.42 and 245.30.1.34";
+    private static final List<String> EXPECTED6 = List.of("127.1.1.0", "192.168.42.42", "245.30.1.34");
+
+    private static final Pattern IP_PATTERN = Pattern.compile("(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)[.]){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)");
+
+    List<String> extractIP(String input) {
+        Matcher matcher = IP_PATTERN.matcher(input);
+        List<String> result = new ArrayList<>();
+        while (matcher.find()) {
+            result.add(matcher.group());
+        }
+        return result;
+    }
+
+    @Test
+    void whenExtractIpAddress_thenCorrect() {
+        assertEquals(EXPECTED1, extractIP(INPUT1));
+        assertEquals(EXPECTED2, extractIP(INPUT2));
+        assertEquals(EXPECTED3, extractIP(INPUT3));
+        assertEquals(EXPECTED4, extractIP(INPUT4));
+        assertEquals(EXPECTED5, extractIP(INPUT5));
+        assertEquals(EXPECTED6, extractIP(INPUT6));
+    }
+}