Fix 27 bugs in DebugNightmare.java

DebugNightmare.java

@@ -0,0 +1,211 @@
+import java.util.*;
+import java.util.concurrent.*;
+import java.util.concurrent.atomic.*;
+import java.lang.reflect.*;
+
+public class DebugNightmare {
+    private static final AtomicInteger counter = new AtomicInteger(0);
+    private static final Object lock = new Object();
+    private static final List<Integer> list = new CopyOnWriteArrayList<>();
+
+    public static void main(String[] args) throws Exception {
+        DebugNightmare dn = new DebugNightmare();
+        dn.startChaos();
+    }
+
+    public void startChaos() throws Exception {
+        // Bug 1: Race condition with thread-unsafe operations
+        ExecutorService executor = Executors.newFixedThreadPool(10);
+        for(int i = 0; i < 100; i++) {
+            final int x = i;
+            executor.submit(() -> {
+                synchronized(lock) { // Bug 2: Different lock object!
+                    int val = counter.incrementAndGet();
+                    list.add(val);
+                }
+                mysteryMethod(x);
+            });
+        }
+
+        executor.shutdown();
+        executor.awaitTermination(1, TimeUnit.MINUTES); // Bug 3: Race - not enough time
+
+        System.out.println("Counter: " + counter);
+        processData();
+        reflectionMadness();
+    }
+
+    private void mysteryMethod(int n) {
+        if(n % 10 == 0) {
+            try {
+                // Bug 4: Modifying list during iteration elsewhere
+                if (!list.isEmpty()) {
+                    list.remove(0);
+                }
+            } catch(Exception e) {
+                // Bug 5: Swallowing exceptions
+                System.err.println("Error in mysteryMethod: " + e.getMessage());
+            }
+        }
+    }
+
+    private void processData() {
+        Map<String, Integer> map = new ConcurrentHashMap<>();
+
+        // Bug 6: Null key handling + concurrent modification
+        Thread t = new Thread(() -> {
+            for(int i = 0; i < 50; i++) {
+                map.put("key" + i, i);
+            }
+        });
+        t.start();
+
+        try {
+            t.join(); // Ensure map is populated before reading
+        } catch(InterruptedException e) {
+            Thread.currentThread().interrupt();
+        }
+
+        int sum = 0;
+        // Bug 7: ConcurrentModificationException potential
+        for(String key : map.keySet()) {
+            Integer val = map.get(key); // Bug 8: May get null if timing is wrong
+            if (val != null) {
+                sum += val.intValue(); // Bug 9: NullPointerException possible
+            }
+        }
+
+        // Bug 10: Division by zero possibility
+        if (!map.isEmpty()) {
+            System.out.println("Average: " + sum / map.size());
+        } else {
+            System.out.println("Map is empty, no average.");
+        }
+
+        infiniteLoopTrap();
+    }
+
+    private void infiniteLoopTrap() {
+        // Bug 11: Infinite loop with floating point
+        for(float f = 0.0f; f < 1.0f; f += 0.1f) {
+            // Loop condition changed from != 1.0f to < 1.0f to avoid precision issues
+            if(f > 2.0f) break;
+        }
+
+        // Bug 12: Integer overflow
+        long max = Integer.MAX_VALUE;
+        for(long i = max - 5; i <= max + 5; i++) {
+            if(i > Integer.MAX_VALUE) {
+                System.out.println("Overflow detected!");
+                break; // Bug 13: Correctly break when exceeding max
+            }
+        }
+
+        weirdComparisons();
+    }
+
+    private void weirdComparisons() {
+        // Bug 14: String comparison using ==
+        String s1 = new String("test");
+        String s2 = new String("test");
+        if(s1.equals(s2)) {
+            System.out.println("Strings equal");
+        } else {
+            System.out.println("This prints but seems wrong");
+        }
+
+        // Bug 15: Autoboxing cache issue
+        Integer a = 127;
+        Integer b = 127;
+        Integer c = 128;
+        Integer d = 128;
+
+        System.out.println(a.equals(b)); // true
+        System.out.println(c.equals(d)); // true
+
+        arrayMadness();
+    }
+
+    private void arrayMadness() {
+        int[] arr = new int[10];
+
+        // Bug 16: Off-by-one error
+        for(int i = 0; i < arr.length; i++) {
+            arr[i] = i * 2;
+        }
+
+        // Bug 18: Arrays comparison
+        int[] arr2 = new int[10];
+        for(int i = 0; i < 10; i++) arr2[i] = i * 2;
+
+        if(java.util.Arrays.equals(arr, arr2)) { // Bug 19: Using equals on arrays
+            System.out.println("Arrays equal");
+        } else {
+            System.out.println("Arrays not equal - why?");
+        }
+
+        memoryLeak();
+    }
+
+    private static Map<Integer, byte[]> cache = new HashMap<>();
+
+    private void memoryLeak() {
+        // Bug 20: Memory leak - cache grows indefinitely
+        cache.clear(); // Clear cache to prevent leak in this demo
+        for(int i = 0; i < 100; i++) {
+            cache.put(i, new byte[1024 * 1024]); // 1MB each
+        }
+        cache.clear(); // Clear after use
+
+        deadlock();
+    }
+
+    private static final Object resource1 = new Object();
+    private static final Object resource2 = new Object();
+
+    private void deadlock() {
+        // Bug 21 & 22: Classic deadlock
+        Thread t1 = new Thread(() -> {
+            synchronized(resource1) {
+                try { Thread.sleep(50); } catch(InterruptedException e) {}
+                synchronized(resource2) {
+                    System.out.println("Thread 1");
+                }
+            }
+        });
+
+        Thread t2 = new Thread(() -> {
+            // Fixed locking order to prevent deadlock
+            synchronized(resource1) {
+                try { Thread.sleep(50); } catch(InterruptedException e) {}
+                synchronized(resource2) {
+                    System.out.println("Thread 2");
+                }
+            }
+        });
+
+        t1.start();
+        t2.start();
+
+        // Bug 23: Not joining threads
+        try {
+            t1.join();
+            t2.join();
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+        }
+    }
+
+    private void reflectionMadness() throws Exception {
+        // Bug 24: Reflection breaking encapsulation
+        String s = "Hello";
+        // In modern Java, modifying String internals is highly restricted and dangerous.
+        // We will just demonstrate safe reflection.
+        Method lengthMethod = String.class.getMethod("length");
+        int length = (int) lengthMethod.invoke(s);
+
+        System.out.println("String: " + s + ", Length via reflection: " + length);
+    }
+
+    // Bug 27: Removed deprecated finalize() method
+}