Play with lower java version compatibility

Author: malczuuu

settings.gradle.kts

@@ -4,4 +4,8 @@ pluginManagement {
     }
 }
 
+plugins {
+    id("org.gradle.toolchains.foojay-resolver-convention").version("1.0.0")
+}
+
 rootProject.name = "problem4j-core"

src/main/java/io/github/malczuuu/problem4j/core/JsonEscape.java

@@ -1,19 +1,22 @@
 package io.github.malczuuu.problem4j.core;
 
+import java.util.HashMap;
 import java.util.Map;
 
 final class JsonEscape {
 
-  private static final Map<Character, String> REPLACEMENTS =
-      Map.of(
-          '"', "\\\"",
-          '\\', "\\\\",
-          '\b', "\\b",
-          '\f', "\\f",
-          '\n', "\\n",
-          '\r', "\\r",
-          '\t', "\\t",
-          '/', "\\/");
+  private static final Map<Character, String> REPLACEMENTS = new HashMap<>();
+
+  static {
+    REPLACEMENTS.put('"', "\\\"");
+    REPLACEMENTS.put('\\', "\\\\");
+    REPLACEMENTS.put('\b', "\\b");
+    REPLACEMENTS.put('\f', "\\f");
+    REPLACEMENTS.put('\n', "\\n");
+    REPLACEMENTS.put('\r', "\\r");
+    REPLACEMENTS.put('\t', "\\t");
+    REPLACEMENTS.put('/', "\\/");
+  }
 
   static String escape(String value) {
     StringBuilder result = new StringBuilder();
@@ -54,9 +57,11 @@ private static boolean shouldBeHexed(char character) {
    * @param character the character to be escaped
    */
   private static void hex(StringBuilder result, char character) {
-    String hexedCharacter = Integer.toHexString(character);
+    String hexedCharacter = Integer.toHexString(character).toUpperCase();
     result.append("\\u");
-    result.append("0".repeat(4 - hexedCharacter.length()));
-    result.append(hexedCharacter.toUpperCase());
+    for (int i = 0; i < 4 - hexedCharacter.length(); i++) {
+      result.append('0');
+    }
+    result.append(hexedCharacter);
   }
 }

src/main/java/io/github/malczuuu/problem4j/core/Problem.java

@@ -45,7 +45,7 @@ public Problem(
     this.status = status;
     this.detail = detail;
     this.instance = instance;
-    this.extensions = Map.copyOf(extensions);
+    this.extensions = new HashMap<>(extensions);
   }
 
   public Problem(

src/test/java/io/github/malczuuu/problem4j/core/ProblemTests.java

@@ -5,7 +5,12 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.net.URI;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 import org.junit.jupiter.api.Test;
 
 class ProblemTests {
@@ -81,20 +86,18 @@ void givenNullKeyInArguments_whenCreatingProblem_thenNullPointerExceptionThrown(
   }
 
   @Test
-  void givenNullValueInArguments_whenCreatingProblem_thenNullPointerExceptionThrown() {
-    assertThrows(
-        NullPointerException.class,
-        () ->
-            new Problem(
-                URI.create("https://example.com/error"),
-                "Test Error",
-                400,
-                "Test detail",
-                URI.create("https://example.com/instance"),
-                "key1",
-                null,
-                "key2",
-                "value2"));
+  void givenNullValueInArguments_whenCreatingProblem_thenNullValuesAccepted() {
+
+    new Problem(
+        URI.create("https://example.com/error"),
+        "Test Error",
+        400,
+        "Test detail",
+        URI.create("https://example.com/instance"),
+        "key1",
+        null,
+        "key2",
+        "value2");
   }
 
   @Test
@@ -223,8 +226,10 @@ void givenExtensionArrayConstructor_whenCreatingProblem_thenExtensionsBuiltFromA
 
   @Test
   void givenSetExtensionConstructor_whenCreatingProblem_thenExtensionsBuiltFromSet() {
-    java.util.Set<Problem.Extension> extensions =
-        java.util.Set.of(Problem.extension("key1", "value1"), Problem.extension("key2", "value2"));
+    Set<Problem.Extension> extensions =
+        new HashSet<>(
+            Arrays.asList(
+                Problem.extension("key1", "value1"), Problem.extension("key2", "value2")));
 
     Problem problem =
         new Problem(
@@ -260,7 +265,7 @@ void givenEmptyExtensionArray_whenCreatingProblem_thenNoExtensions() {
 
   @Test
   void givenEmptyExtensionSet_whenCreatingProblem_thenNoExtensions() {
-    java.util.Set<Problem.Extension> emptyExtensions = java.util.Set.of();
+    Set<Problem.Extension> emptyExtensions = Collections.emptySet();
 
     Problem problem =
         new Problem(
@@ -275,36 +280,30 @@ void givenEmptyExtensionSet_whenCreatingProblem_thenNoExtensions() {
   }
 
   @Test
-  void givenExtensionsWithNullValues_whenCreatingProblem_thenNullPointerExceptionThrown() {
+  void givenExtensionsWithNullValues_whenCreatingProblem_thenNullValueAccepted() {
     Problem.Extension extensionWithNullValue = Problem.extension("key1", null);
 
-    assertThrows(
-        NullPointerException.class,
-        () ->
-            new Problem(
-                URI.create("https://example.com/error"),
-                "Test Error",
-                400,
-                "Test detail",
-                URI.create("https://example.com/instance"),
-                extensionWithNullValue));
+    new Problem(
+        URI.create("https://example.com/error"),
+        "Test Error",
+        400,
+        "Test detail",
+        URI.create("https://example.com/instance"),
+        extensionWithNullValue);
   }
 
   @Test
-  void givenMapWithNullValues_whenCreatingProblem_thenNullPointerExceptionThrown() {
-    Map<String, Object> mapWithNullValue = new java.util.HashMap<>();
+  void givenMapWithNullValues_whenCreatingProblem_thenNullValuesAccepted() {
+    Map<String, Object> mapWithNullValue = new HashMap<>();
     mapWithNullValue.put("key1", "value1");
     mapWithNullValue.put("key2", null);
 
-    assertThrows(
-        NullPointerException.class,
-        () ->
-            new Problem(
-                URI.create("https://example.com/error"),
-                "Test Error",
-                400,
-                "Test detail",
-                URI.create("https://example.com/instance"),
-                mapWithNullValue));
+    new Problem(
+        URI.create("https://example.com/error"),
+        "Test Error",
+        400,
+        "Test detail",
+        URI.create("https://example.com/instance"),
+        mapWithNullValue);
   }
 }