From ae5bf3ddb11878cd9dfb00ab5b2f388006ecb567 Mon Sep 17 00:00:00 2001
From: "@hangga" <bazeniancode@gmail.com>
Date: Sun, 11 Feb 2024 18:38:26 +0700
Subject: [PATCH] update experiment

---
 .../UUIDPositiveLongGeneratorUnitTest.java    | 70 ++++++++++++-------
 1 file changed, 43 insertions(+), 27 deletions(-)

diff --git a/core-java-modules/core-java-uuid/src/test/java/com/baeldung/uuid/UUIDPositiveLongGeneratorUnitTest.java b/core-java-modules/core-java-uuid/src/test/java/com/baeldung/uuid/UUIDPositiveLongGeneratorUnitTest.java
index a4d57b19c2..322d93444d 100644
--- a/core-java-modules/core-java-uuid/src/test/java/com/baeldung/uuid/UUIDPositiveLongGeneratorUnitTest.java
+++ b/core-java-modules/core-java-uuid/src/test/java/com/baeldung/uuid/UUIDPositiveLongGeneratorUnitTest.java
@@ -1,43 +1,59 @@
 package com.baeldung.uuid;
 
+import com.fasterxml.uuid.impl.UUIDUtil;
 import org.junit.jupiter.api.Test;
 
-import java.lang.reflect.Method;
-import java.util.HashSet;
-import java.util.Set;
+import java.util.UUID;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
 public class UUIDPositiveLongGeneratorUnitTest {
 
-    private final UUIDPositiveLongGenerator uuidLongGenerator = new UUIDPositiveLongGenerator();
+    private void verifyUUID(UUID uuid) {
+        byte[] bytes = toByteArray(uuid);
 
-    private final Set<Long> uniqueValues = new HashSet<>();
+        // assert that byte at index 6 is 0x40 (version 4)
+        byte byte6 = bytes[6];
+        assertThat(byte6 & 0xF0).isEqualTo(0x40);
+
+        // assert that the byte at index 8 is 0x80 (IETF type variant)
+        byte byte8 = bytes[8];
+        assertThat(byte8 & 0xC0).isEqualTo(0x80);
+    }
+
+    private boolean[] getFirst122Bits(UUID uuid) {
+        long msb = uuid.getMostSignificantBits();
+        boolean[] bits = new boolean[122]; // Untuk menyimpan 122 bit pertama dari UUID
+
+        // Konversi 64 bit pertama (Most Significant Bits) menjadi bit
+        for (int i = 0; i < 64; i++) {
+            bits[i] = ((msb >> (63 - i)) & 1) == 1; // Mendapatkan nilai bit ke-i
+        }
+        return bits;
+    }
+
+    private byte[] toByteArray(UUID uuid) {
+        long msb = uuid.getMostSignificantBits();
+        long lsb = uuid.getLeastSignificantBits();
+        byte[] buffer = new byte[16];
+        for (int i = 0; i < 8; i++) {
+            buffer[i] = (byte) (msb >>> 8 * (7 - i));
+        }
+        for (int i = 8; i < 16; i++) {
+            buffer[i] = (byte) (lsb >>> 8 * (7 - i));
+        }
+        return buffer;
+    }
 
     @Test
-    void whenForeachMethods_thenRetryWhileNotUnique() throws Exception {
-        for (Method method : uuidLongGenerator.getClass().getDeclaredMethods()) {
-            long uniqueValue;
-            do uniqueValue = (long) method.invoke(uuidLongGenerator); while (!isUnique(uniqueValue));
-            assertThat(uniqueValue).isPositive();
+    public void whenGivenUUID_thenVerified() {
+        for (int i = 0; i < 100; i++) {
+            UUID uuid = UUID.randomUUID();
+            verifyUUID(uuid);
+
+            long msbfirst = uuid.getMostSignificantBits() >>> 6;
+            System.out.println(msbfirst);
         }
     }
 
-    @Test
-    void whenGivenLongValue_thenCheckUniqueness() {
-        long uniqueValue = generateUniqueLong();
-        assertThat(uniqueValue).isPositive();
-    }
-
-    private long generateUniqueLong() {
-        long uniqueValue;
-        do uniqueValue = uuidLongGenerator.combineBitwise(); while (!isUnique(uniqueValue));
-        return uniqueValue;
-    }
-
-    private boolean isUnique(long value) {
-        // Implement uniqueness checking logic, for example, by checking in the database
-        return uniqueValues.add(value);
-    }
-
 }