public boolean equals(Object obj) {
    return (this == obj);
}

public int hashCode() {
    int h = hash;
    if (h == 0 && value.length > 0) {
        char val[] = value;

        for (int i = 0; i < value.length; i++) {
            h = 31 * h + val[i];
        }
        hash = h;
    }
    return h;
}

public class HashMap<K,V> extends AbstractMap<K,V>
    implements Map<K,V>, Cloneable, Serializable {
    ···

    public V put(K key, V value) {
        return putVal(hash(key), key, value, false, true);
    }
    ···

    public V get(Object key) {
        Node<K,V> e;
        return (e = getNode(hash(key), key)) == null ? null : e.value;
    }
    ···
}

public class Hashtable<K,V>
    extends Dictionary<K,V>
    implements Map<K,V>, Cloneable, java.io.Serializable {
    ···

    public synchronized V put(K key, V value) {
        // Make sure the value is not null
        if (value == null) {
            throw new NullPointerException();
        }

        ···
        addEntry(hash, key, value, index);
        return null;
    }
    ···

    public synchronized V get(Object key) {
        HashtableEntry<?,?> tab[] = table;
        int hash = key.hashCode();
        int index = (hash & 0x7FFFFFFF) % tab.length;
        for (HashtableEntry<?,?> e = tab[index] ; e != null ; e = e.next) {
            if ((e.hash == hash) && e.key.equals(key)) {
                return (V)e.value;
            }
        }
        return null;
    }
    ···
}

Segment<K,V> s = (Segment<K,V>)UNSAFE.getObjectVolatile(segments, u)

HashEntry<K,V> e = (HashEntry<K,V>) UNSAFE.getObjectVolatile
  (tab, ((long)(((tab.length - 1) & h)) << TSHIFT) + TBASE)

final V putVal(K key, V value, boolean onlyIfAbsent) {
    if (key == null || value == null) throw new NullPointerException();
    int hash = spread(key.hashCode());
    int binCount = 0;
    for (Node<K,V>[] tab = table;;) {
        Node<K,V> f; int n, i, fh;
        if (tab == null || (n = tab.length) == 0)
            tab = initTable();
        else if ((f = tabAt(tab, i = (n - 1) & hash)) == null) {
            if (casTabAt(tab, i, null,
                            new Node<K,V>(hash, key, value, null)))
                break;                   // no lock when adding to empty bin
        }
        else if ((fh = f.hash) == MOVED)
            tab = helpTransfer(tab, f);
        else {
            V oldVal = null;
            synchronized (f) {
                if (tabAt(tab, i) == f) {
                    if (fh >= 0) {
                        binCount = 1;
                        ···
                    }
                    else if (f instanceof TreeBin) {
                       ···
                    }
                    else if (f instanceof ReservationNode)
                        throw new IllegalStateException("Recursive update");
                }
            }
            ···
    }
    addCount(1L, binCount);
    return null;
}

public class ArrayList<E> extends AbstractList<E>
        implements List<E>, RandomAccess, Cloneable, java.io.Serializable
    ···

    // 增加元素
    public boolean add(E e) {
        ensureCapacityInternal(size + 1);  // Increments modCount!!
        elementData[size++] = e;
        return true;
    }
    ···

    // 删除元素
    public E remove(int index) {
        if (index >= size)
            throw new IndexOutOfBoundsException(outOfBoundsMsg(index));

        modCount++;
        E oldValue = (E) elementData[index];

        int numMoved = size - index - 1;
        if (numMoved > 0)
            System.arraycopy(elementData, index+1, elementData, index,
                             numMoved);
        elementData[--size] = null; // clear to let GC do its work

        return oldValue;
    }
    ···

    // 查找元素
    public E get(int index) {
        if (index >= size)
            throw new IndexOutOfBoundsException(outOfBoundsMsg(index));

        return (E) elementData[index];
    }
    ···
}

public class LinkedList<E>
    extends AbstractSequentialList<E>
    implements List<E>, Deque<E>, Cloneable, java.io.Serializable
{
    ····

    private static class Node<E> {
        E item;
        Node<E> next;
        Node<E> prev;

        Node(Node<E> prev, E element, Node<E> next) {
            this.item = element;
            this.next = next;
            this.prev = prev;
        }
    }
    ···
    
    // 增加元素
    void linkLast(E e) {
        final Node<E> l = last;
        final Node<E> newNode = new Node<>(l, e, null);
        last = newNode;
        if (l == null)
            first = newNode;
        else
            l.next = newNode;
        size++;
        modCount++;
    }
    ···

    // 删除元素
    E unlink(Node<E> x) {
        final E element = x.item;
        final Node<E> next = x.next;
        final Node<E> prev = x.prev;

        if (prev == null) {
            first = next;
        } else {
            prev.next = next;
            x.prev = null;
        }

        if (next == null) {
            last = prev;
        } else {
            next.prev = prev;
            x.next = null;
        }

        x.item = null;
        size--;
        modCount++;
        return element;
    }
    ···

    // 查找元素
    Node<E> node(int index) {
        // assert isElementIndex(index);

        if (index < (size >> 1)) {
            Node<E> x = first;
            for (int i = 0; i < index; i++)
                x = x.next;
            return x;
        } else {
            Node<E> x = last;
            for (int i = size - 1; i > index; i--)
                x = x.prev;
            return x;
        }
    }
    ···
}

public class CopyOnWriteArrayList<E>
    implements List<E>, RandomAccess, Cloneable, java.io.Serializable {
 
    final transient Object lock = new Object();
    ···

    // 增加元素
    public boolean add(E e) {
        synchronized (lock) {
            Object[] elements = getArray();
            int len = elements.length;
            Object[] newElements = Arrays.copyOf(elements, len + 1);
            newElements[len] = e;
            setArray(newElements);
            return true;
        }
    }
    ···

    // 删除元素
    public E remove(int index) {
        synchronized (lock) {
            Object[] elements = getArray();
            int len = elements.length;
            E oldValue = get(elements, index);
            int numMoved = len - index - 1;
            if (numMoved == 0)
                setArray(Arrays.copyOf(elements, len - 1));
            else {
                Object[] newElements = new Object[len - 1];
                System.arraycopy(elements, 0, newElements, 0, index);
                System.arraycopy(elements, index + 1, newElements, index,
                                 numMoved);
                setArray(newElements);
            }
            return oldValue;
        }
    }
    ···
    
    // 查找元素
    private E get(Object[] a, int index) {
        return (E) a[index];
    }
}

try {
    Class cls = Class.forName("com.jasonwu.Test");
    //获取构造方法
    Constructor[] publicConstructors = cls.getConstructors();
    //获取全部构造方法
    Constructor[] declaredConstructors = cls.getDeclaredConstructors();
    //获取公开方法
    Method[] methods = cls.getMethods();
    //获取全部方法
    Method[] declaredMethods = cls.getDeclaredMethods();
    //获取公开属性
    Field[] publicFields = cls.getFields();
    //获取全部属性
    Field[] declaredFields = cls.getDeclaredFields();
    Object clsObject = cls.newInstance();
    Method method = cls.getDeclaredMethod("getModule1Functionality");
    Object object = method.invoke(null);
} catch (ClassNotFoundException e) {
    e.printStackTrace();
} catch (IllegalAccessException e) {
    e.printStackTrace();
} catch (InstantiationException e) {
    e.printStackTrace();
} catch (NoSuchMethodException e) {
    e.printStackTrace();
} catch (InvocationTargetException e) {
    e.printStackTrace();
}

public class CustomManager {
    private Context mContext;
    private static final Object mLock = new Object();
    private static CustomManager mInstance;

    public static CustomManager getInstance(Context context) {
        synchronized (mLock) {
            if (mInstance == null) {
                mInstance = new CustomManager(context);
            }

            return mInstance;
        }
    }

    private CustomManager(Context context) {
        this.mContext = context.getApplicationContext();
    }
}

public class CustomManager {
    private Context mContext;
    private volatile static CustomManager mInstance;

    public static CustomManager getInstance(Context context) {
        // 避免非必要加锁
        if (mInstance == null) {
            synchronized (CustomManger.class) {
                if (mInstance == null) {
                    mInstacne = new CustomManager(context);
                }
            }
        }

        return mInstacne;
    }

    private CustomManager(Context context) {
        this.mContext = context.getApplicationContext();
    }
}

public class CustomManager{
    private CustomManager(){}
 
    private static class CustomManagerHolder {
        private static final CustomManager INSTANCE = new CustomManager();
    }
 
    public static CustomManager getInstance() {
        return CustomManagerHolder.INSTANCE;
    } 
}

public interface Lock {
    void lock();
    void lockInterruptibly() throws InterruptedException;  
    boolean tryLock();  
    boolean tryLock(long time, TimeUnit unit) throws InterruptedException;  
    void unlock();  
    Condition newCondition();
}

// 定义相关接口
public interface BaseInterface {
    void doSomething();
}

// 接口的相关实现类
public class BaseImpl implements BaseInterface {
    @Override
    public void doSomething() {
        System.out.println("doSomething");
    }
}

public static void main(String args[]) {
    BaseImpl base = new BaseImpl();
    // Proxy 动态代理实现
    BaseInterface proxyInstance = (BaseInterface) Proxy.newProxyInstance(base.getClass().getClassLoader(), base.getClass().getInterfaces(), new InvocationHandler() {
        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            if (method.getName().equals("doSomething")) {
                method.invoke(base, args);
                System.out.println("do more");
            }
            return null;
        }
    });

    proxyInstance.doSomething();
}

public class Proxy implements java.io.Serializable {

    // 代理类的缓存
    private static final WeakCache<ClassLoader, Class<?>[], Class<?>>
        proxyClassCache = new WeakCache<>(new KeyFactory(), new ProxyClassFactory());
    ···

    // 生成代理对象方法入口
    public static Object newProxyInstance(ClassLoader loader,
                                        Class<?>[] interfaces,
                                        InvocationHandler h)
    throws IllegalArgumentException
    {
        Objects.requireNonNull(h);

        final Class<?>[] intfs = interfaces.clone();
        // 找到并生成相关的代理类
        Class<?> cl = getProxyClass0(loader, intfs);

        // 调用代理类的构造方法生成代理类实例
        try {
            final Constructor<?> cons = cl.getConstructor(constructorParams);
            final InvocationHandler ih = h;
            if (!Modifier.isPublic(cl.getModifiers())) {
                cons.setAccessible(true);
            }
            return cons.newInstance(new Object[]{h});
        } 
        ···
    }
    ···
    
    // 定义和返回代理类的工厂类
    private static final class ProxyClassFactory
        implements BiFunction<ClassLoader, Class<?>[], Class<?>>
    {
        // 所有代理类的前缀
        private static final String proxyClassNamePrefix = "$Proxy";

        //  用于生成唯一代理类名称的下一个数字
        private static final AtomicLong nextUniqueNumber = new AtomicLong();

        @Override
        public Class<?> apply(ClassLoader loader, Class<?>[] interfaces) {

            Map<Class<?>, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.length);
            ···

            String proxyPkg = null;     // 用于定义代理类的包名
            int accessFlags = Modifier.PUBLIC | Modifier.FINAL;

            // 确保所有 non-public 的代理接口在相同的包里
            for (Class<?> intf : interfaces) {
                int flags = intf.getModifiers();
                if (!Modifier.isPublic(flags)) {
                    accessFlags = Modifier.FINAL;
                    String name = intf.getName();
                    int n = name.lastIndexOf('.');
                    String pkg = ((n == -1) ? "" : name.substring(0, n + 1));
                    if (proxyPkg == null) {
                        proxyPkg = pkg;
                    } else if (!pkg.equals(proxyPkg)) {
                        throw new IllegalArgumentException(
                            "non-public interfaces from different packages");
                    }
                }
            }

            if (proxyPkg == null) {
                // 如果没有 non-public 的代理接口，使用默认的包名
                proxyPkg = "";
            }

            {
                List<Method> methods = getMethods(interfaces);
                Collections.sort(methods, ORDER_BY_SIGNATURE_AND_SUBTYPE);
                validateReturnTypes(methods);
                List<Class<?>[]> exceptions = deduplicateAndGetExceptions(methods);

                Method[] methodsArray = methods.toArray(new Method[methods.size()]);
                Class<?>[][] exceptionsArray = exceptions.toArray(new Class<?>[exceptions.size()][]);

                // 生成代理类的名称
                long num = nextUniqueNumber.getAndIncrement();
                String proxyName = proxyPkg + proxyClassNamePrefix + num;

                // Android 特定修改：直接调用 native 方法生成代理类
                return generateProxy(proxyName, interfaces, loader, methodsArray,
                                     exceptionsArray);

                // JDK 使用的 ProxyGenerator.generateProxyClas 方法创建代理类
                byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
                    proxyName, interfaces, accessFlags);
                try {
                    return defineClass0(loader, proxyName,
                                        proxyClassFile, 0, proxyClassFile.length);
                } ···
        }
    }
    ···

    // 最终调用 native 方法生成代理类
    @FastNative
    private static native Class<?> generateProxy(String name, Class<?>[] interfaces,
                                                 ClassLoader loader, Method[] methods,
                                                 Class<?>[][] exceptions);

}

public static byte[] generateProxyClass(final String name,
                                        Class[] interfaces)
{
    ProxyGenerator gen = new ProxyGenerator(name, interfaces);
    final byte[] classFile = gen.generateClassFile();

    if (saveGeneratedFiles) {
        java.security.AccessController.doPrivileged(
        new java.security.PrivilegedAction<Void>() {
            public Void run() {
                try {
                    FileOutputStream file =
                        new FileOutputStream(dotToSlash(name) + ".class");
                    file.write(classFile);
                    file.close();
                    return null;
                } catch (IOException e) {
                    throw new InternalError(
                        "I/O exception saving generated file: " + e);
                }
            }
        });
    }

    return classFile;
}