1.原型模式的定义及使用场景

定义：用原型实例指定创建对象的种类，并通过拷贝这些原型创建新的对象 使用场景： 1）类初始化需要消耗非常多的资源，这个资源包括数据、硬件资源等，通过原型拷贝避免这些消耗 2）通过new产生一个对象需要非常繁琐的数据准备或访问权限，这时可以使用原型模式

3）一个对象需要提供给其他对象访问，而且各个调用者可能都需要修改其值时，可以考虑使用原型模式拷贝多个对象供调用者使用，即保护性拷贝

2.原型模式的优缺点

2.1优点

性能优良 原型模式是在内存二进制流的拷贝，要比直接new一个对象性能好，特别是要在一个循环体内产生大量的对象时，原型模式可以更好地体现其优点

2.2缺点

逃避构造函数的约束 这既是他的优点也是缺点，直接在内存中拷贝，构造函数不会执行。需要在实际应用时考虑

3.注意实现

1）构造函数默认不执行 2）浅拷贝及深拷贝 Object类提供的方法clone只是拷贝本对象，其对象内部的数组、引用对象等都不拷贝，还是指向原型对象的内部元素地址，这种拷贝为浅拷贝。如需要深拷贝，对应的成员也需指向clone方法 3）要使用clone方法，类的成员变量上不要增加final关键字

4.原型模式的实现方式

ProtoType： public class ProtoType implements Cloneable { public ProtoType() { System.out.println("ProtoType is excute..."); } private int id; private String name; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override protected ProtoType clone() { ProtoType protoType = null; try { protoType = (ProtoType) super.clone(); } catch (CloneNotSupportedException e) { e.printStackTrace(); } return protoType; } @Override public String toString() { return "ProtoType{" + "id=" + id + ", name='" + name + '\'' + '}'; } } Text： public class Test { public static void main(String args[]) { ProtoType type = new ProtoType(); type.setId(1); type.setName("张三"); System.out.println(type); ProtoType clone = type.clone(); clone.setId(2); clone.setName("李四"); System.out.println(clone); } } Objec的clone源码： /** * Creates and returns a copy of this {@code Object}. The default * implementation returns a so-called "shallow" copy: It creates a new * instance of the same class and then copies the field values (including * object references) from this instance to the new instance. A "deep" copy, * in contrast, would also recursively clone nested objects. A subclass that * needs to implement this kind of cloning should call {@code super.clone()} * to create the new instance and then create deep copies of the nested, * mutable objects. * * @return a copy of this object. * @throws CloneNotSupportedException * if this object's class does not implement the {@code * Cloneable} interface. */ protected Object clone() throws CloneNotSupportedException { if (!(this instanceof Cloneable)) { throw new CloneNotSupportedException("Class " + getClass().getName() + " doesn't implement Cloneable"); } return internalClone(); } /* * Native helper method for cloning. */ private native Object internalClone(); 可见执行了一个native方法执行二进制流的拷贝

5.原型模式在Android中的实际应用

Intent： @Override public Object clone() { return new Intent(this); } /** * Copy constructor. */ public Intent(Intent o) { this.mAction = o.mAction; this.mData = o.mData; this.mType = o.mType; this.mPackage = o.mPackage; this.mComponent = o.mComponent; this.mFlags = o.mFlags; this.mContentUserHint = o.mContentUserHint; if (o.mCategories != null) { this.mCategories = new ArraySet<String>(o.mCategories); } if (o.mExtras != null) { this.mExtras = new Bundle(o.mExtras); } if (o.mSourceBounds != null) { this.mSourceBounds = new Rect(o.mSourceBounds); } if (o.mSelector != null) { this.mSelector = new Intent(o.mSelector); } if (o.mClipData != null) { this.mClipData = new ClipData(o.mClipData); } }