StringInterner

src/main/java/com/github/_1c_syntax/utils/StringInterner.java

@@ -0,0 +1,18 @@
+package com.github._1c_syntax.utils;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class StringInterner {
+
+  private final Map<String, String> map = new ConcurrentHashMap<>();
+
+  public String intern(String string) {
+    String exist = map.putIfAbsent(string, string);
+    return (exist == null) ? string : exist;
+  }
+
+  public void clear() {
+    map.clear();
+  }
+}

src/test/java/com/github/_1c_syntax/utils/StringInternerTest.java

@@ -0,0 +1,54 @@
+package com.github._1c_syntax.utils;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class StringInternerTest {
+
+  private StringInterner interner;
+
+  @BeforeEach
+  public void init() {
+    interner = new StringInterner();
+  }
+
+  @Test
+  void testIntern() {
+    //given
+    String s1 = new String("1");
+    String s2 = new String("1");
+
+    // when
+    var intern1 = interner.intern(s1);
+
+    // then
+    assertEquals(s1, intern1);
+
+    // when
+    var intern2 = interner.intern(s2);
+
+    // then
+    assertEquals(s1, intern2);
+  }
+
+  @Test
+  void testClear() {
+
+    //given
+    String s1 = new String("1");
+    String s2 = new String("1");
+
+    interner.intern(s1);
+
+    // when
+    interner.clear();
+
+    // when
+    var intern = interner.intern(s2);
+
+    // then
+    assertEquals(s2, intern);
+  }
+}