[TOC] ## 單例模式 ~~~ public class Singleton { private volatile static Singleton singleton; private Singleton (){} public static Singleton getSingleton() { if (singleton == null) { synchronized (Singleton.class) { if (singleton == null) { singleton = new Singleton(); } } } return singleton; } } ~~~ ## 工廠模式 ~~~ public interface IProduct{ public void use()； } public class ProductA implements IProduct { public void use(){ System.out.println("use A"); } } public class ProductB implements IProduct { public void use(){ System.out.println("use B"); } ~~~ ### 普通工廠模式 ~~~ public class MyFactory{ public IProduct create(String type){ if("A".equals(type)){ return new ProductA(); }else if("B".equals(type)){ return new ProductB(); } } } ~~~ ### 多個工廠方法模式 ~~~ public class MyFactory{ public IProduct createA(){ return new ProductA(); } public IProduct createB(){ return new ProductB(); } } ~~~ ### 抽象工廠模式 ~~~ public interface IFactory{ public IProduct create(); } public class FactoryA implements IFactory{ public IProduct create(){ return new ProductA(); } } public class FactoryB implements IFactory{ public IProduct create(){ return new ProductB(); } } public void test(){ IFactory factoryA = new FactoryA(); IProduct productA = factoryA.create(); ~~~ ## 生產者消費者模型 生產者生產數據到緩沖區中，消費者從緩沖區中取數據。 如果緩沖區已經滿了，則生產者線程阻塞； 如果緩沖區為空，那么消費者線程阻塞。 ~~~ public interface ITaskQueue{ public void add(); public int remove(); } public class Consumer extends Thread{ ITaskQueue queue; public Consumer(ITaskQueue queue){ this.queue = queue; } public void run(){ while(true){ try { Thread.sleep((long) (1000 * Math.random())); } catch (InterruptedException e) { e.printStackTrace(); } queue.remove(); } } } public class Producer extends Thread{ ITaskQueue queue; public Producer(ITaskQueue queue){ this.queue = queue; } public void run(){ while(true){ try { Thread.sleep((long) (1000 * Math.random())); } catch (InterruptedException e) { e.printStackTrace(); } queue.add(); } } ~~~ ### 使用synchronized wait notify ~~~ public void TaskQueue1 implements ITaskQueue{ //當前資源數量 private int num = 0; //資源池中允許存放的資源數目 private int size = 10; public synchronized void add(){ if(num >= size){ wait(); }else{ num ++; notifyAll(); } } public synchronized void remove(){ if(num <= 0){ wait(); }else{ num --; notifyAll(); } } } ~~~ ### 使用BlockingQueue ~~~ public void TaskQueue2 implements ITaskQueue{ private ArrayBlockingQueue<Integer> queue = new ArrayBlockingQueue<>(); public void add(){ queue.put(1); } public void remove(){ queue.talke(); } } ~~~ ## 手寫json解析 ### 解法1 [https://github.com/5A59/JsonParser](https://github.com/5A59/JsonParser) #### Reader ~~~ public class Reader { private char[] buffer; private int pos; public Reader(String json) { buffer = json.toCharArray(); pos = 0; } public char next() throws BufferException{ if (pos < buffer.length){ return buffer[pos]; } throw new BufferException("no next"); } public void skipNext() { pos ++; } public void moveToLast() { pos --; } public String nextName() { //讀取下一個名稱 知道遇到下一個 '"' return nextString(); } //讀取下一個value 根據類型的區別 分為 nextBoolean() nextDouble() nextFloat()... public String nextNumString() { nextNonWhitespace(); StringBuilder stringBuilder = new StringBuilder(); char c; while (pos < buffer.length){ c = buffer[pos ++]; if (c == '"' && stringBuilder.length() <= 0){ continue; }else if (c > '0' && c < '9' || c == '.' || c == '-'){ stringBuilder.append(c); }else { pos --; break; } } return stringBuilder.toString(); } } ~~~ #### Parser ~~~ public interface Parser { Object parse(Reader reader); } ~~~ 解析器安裝類型可以分為 ObjectParser , PrimitiveParser(基本類型) , ArrayParser , NullParser 下面以ObjectParser為例 #### ObjectParser ~~~ public class ObjectParser implements Parser { private static final int START_TAG = -1; private static final int OBJECT = 0; private static final int NAME = 1; private static final int VALUE = 2; private Stack<Integer> stack;//核心操作棧 private Stack<String> nameStack;//名稱張 private Class<?> raw; private Map<String, Field> map; // <fieldName, typeName> private Map<String, Object> map; // <fieldName, typeName> public ObjectParser(Class<?> raw) { this.raw = raw; map = new HashMap<>(); stack = new Stack<>(); nameStack = new Stack<>(); } public Object parse(Reader reader) { //一次性class對象解析，存入map Field[] fields = raw.getDeclaredFields(); for (Field f : fields){ String name = f.getName(); map.put(name, f); } Object instance; try { instance = raw.newInstance(); } catch (Exception e) { return null; } stack.push(START_TAG); while (reader.hasNext() && !stack.empty()){ //為了第一次能往下執行初始化 if (stack.peek() == START_TAG){ stack.pop(); } char c; try { c = reader.next(); } catch (Reader.BufferException e) { e.printStackTrace(); break ; } reader.skipNext(); Logger.d("c is " + c); switch (c){ case '{': if (stack != null && !stack.isEmpty() && stack.peek() == VALUE){ //如果是value reader.moveToLast(); setValue(reader, instance); }else { //否則就是key stack.push(OBJECT); stack.push(NAME); } continue; case '"': if (stack.peek() == NAME){ //如果是name String name = reader.nextName(); nameStack.push(name); stack.pop(); }else if (stack.peek() == VALUE){ //如果是value setValue(reader, instance); } break; case ',': stack.push(NAME); break; case ':': stack.push(VALUE); break; case '}': if (stack.peek() == OBJECT){ stack.pop(); } break; case ' ': case '\n': break; default: reader.moveToLast(); setNameAndValue(reader, instance); break; } } return instance; } private void setValue(Reader reader, Object instance) { //根據類型的不同 初始化不同的 使用不同Parser //通過反射Field的值調用不同的值Par ~~~ 核心思想： 維護一個操作指令棧 [自己動手實現一個簡單的JSON解析器](https://www.cnblogs.com/nullllun/p/8358146.html#autoid-1-0-0)