Used hash-based lookup rather than linear search

jackson-datatype-problem/src/main/java/org/zalando/problem/ProblemModule.java

@@ -6,6 +6,7 @@
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import org.apiguardian.api.API;
 
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -88,7 +89,7 @@ private static <E extends Enum & StatusType> Map<Integer, StatusType> buildIndex
             }
         }
 
-        return index;
+        return Collections.unmodifiableMap(index);
     }
 
     public ProblemModule withStackTraces() {

problem/src/main/java/org/zalando/problem/Status.java

@@ -3,8 +3,14 @@
 import org.apiguardian.api.API;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.Arrays;
+import java.util.Collections;
+import java.util.Map;
 
+import static java.util.function.Function.identity;
+import static java.util.stream.Collectors.collectingAndThen;
+import static java.util.stream.Collectors.toMap;
 import static org.apiguardian.api.API.Status.MAINTAINED;
 
 /**
@@ -261,6 +267,12 @@ public enum Status implements StatusType {
      * @see <a href="http://tools.ietf.org/html/rfc6585#section-6">Additional HTTP Status Codes</a>
      */
     NETWORK_AUTHENTICATION_REQUIRED(511, "Network Authentication Required");
+
+    private static final Map<Integer, Status> STATUSES = Arrays.stream(values())
+            .collect(collectingAndThen(
+                    toMap(Status::getStatusCode, identity()),
+                    Collections::unmodifiableMap));
+
     private final int code;
     private final String reason;
 
@@ -269,20 +281,6 @@ public enum Status implements StatusType {
         this.reason = reasonPhrase;
     }
 
-    /**
-     * Creates a Status instance from the given code.
-     *
-     * @param code the HTTP code as a number
-     * @return the correct enum value for this status code.
-     * @throws IllegalArgumentException if the given code does not correspond to a known HTTP status.
-     */
-    public static Status ofCode(int code) {
-        return Arrays.stream(Status.values())
-                .filter(status -> status.getStatusCode() == code)
-                .findFirst()
-                .orElseThrow(() -> new IllegalArgumentException("There is no known status for this code (" + code + ")."));
-    }
-
     /**
      * Get the associated status code.
      *
@@ -313,4 +311,22 @@ public String getReasonPhrase() {
     public String toString() {
         return getStatusCode() + " " + getReasonPhrase();
     }
+
+    /**
+     * Creates a Status instance from the given code.
+     *
+     * @param code the HTTP code as a number
+     * @return the correct enum value for this status code.
+     * @throws IllegalArgumentException if the given code does not correspond to a known HTTP status.
+     */
+    public static Status valueOf(final int code) {
+        @Nullable final Status status = STATUSES.get(code);
+
+        if (status == null) {
+            throw new IllegalArgumentException("There is no known status for this code (" + code + ").");
+        }
+
+        return status;
+    }
+
 }

problem/src/test/java/org/zalando/problem/StatusTest.java

@@ -1,18 +1,18 @@
 package org.zalando.problem;
 
-import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.CsvSource;
 
 import java.util.stream.Stream;
 
 import static org.hamcrest.MatcherAssert.assertThat;
-import static org.hamcrest.Matchers.*;
 import static org.hamcrest.Matchers.emptyOrNullString;
+import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.not;
 import static org.hobsoft.hamcrest.compose.ComposeMatchers.hasFeature;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 
 final class StatusTest {
@@ -25,9 +25,7 @@ void shouldHaveReasonPhrase() {
 
     @Test
     void shouldHaveMeaningfulToString() {
-        Status notFound = Status.NOT_FOUND;
-
-        assertThat(notFound.toString(), equalTo("404 Not Found"));
+        assertThat(Status.NOT_FOUND.toString(), equalTo("404 Not Found"));
     }
 
     @ParameterizedTest
@@ -37,17 +35,16 @@ void shouldHaveMeaningfulToString() {
             "200, OK",
             "500, Internal Server Error"
     })
-    void shouldHaveCorrectValueFromCode(int code, String line) {
-        Status statusFromCode = Status.ofCode(code);
+    void shouldHaveCorrectValueFromCode(final int statusCode, final String reasonPhrase) {
+        final Status status = Status.valueOf(statusCode);
 
-        assertThat(statusFromCode.getStatusCode(), equalTo(code));
-        assertThat(statusFromCode.getReasonPhrase(), equalTo(line));
+        assertThat(status.getStatusCode(), equalTo(statusCode));
+        assertThat(status.getReasonPhrase(), equalTo(reasonPhrase));
     }
 
     @Test
     void shouldThrowOnNonExistingCode() {
-        Assertions.assertThrows(IllegalArgumentException.class, () -> {
-            Status.ofCode(111);
-        });
+        assertThrows(IllegalArgumentException.class, () -> Status.valueOf(111));
     }
+
 }