java對象實例化的方式有以下幾種：
1、使用new
2、工廠模式
3、反射
4、clone()方法
5、反序列化方式

/**

• 實現Cloneable和Serializable接口

• */
  public class Book implements Cloneable, Serializable {
  private static final long serialVersionUID = 1L;

  private Integer serialNum; // 序列號
  private String name; // 圖書名稱

  public Book() {
  System.out.println("默認構造函數");
  }

  public Book(Integer serialNum, String name) {
  System.out.println("帶參數構造函數");
  this.serialNum = serialNum;
  this.name = name;
  }

  public int getSerialNum() {
  return serialNum;
  }
  public void setSerialNum(int serialNum) {
  this.serialNum = serialNum;
  }
  public String getName() {
  return name;
  }
  public void setName(String name) {
  this.name = name;
  }

  @Override
  public String toString() {
  if (name == null) {
  return "書籍屬性還未填寫";
  }

  return serialNum + " : " + name;

  }

  @Override
  protected Object clone() throws CloneNotSupportedException {
  return super.clone();
  }
  }

class BookFactory {
public static Book getInstance(Integer serialNum, String name) {
return new Book(serialNum, name);
}
}

public class Instantiation {

// 1.通過new實例化對象 public static Book newMode() {System.out.println("============================================================");System.out.println("通過new實例化對象");Book book = new Book(1, "大道揚帆");return book; }// 2.通過工廠方式實例化對象，其本質還是new，但將實例化的細節交給了工廠來處理，屏蔽了和業務代碼無關的功能，一定程度上實現了和業務代碼的解耦 public static Book factoryMode() {System.out.println("============================================================");System.out.println("通過工廠方式實例化對象");return BookFactory.getInstance(2, "大道揚帆"); }// 3.通過反射方式實例化對象 @SuppressWarnings("rawtypes") public static Book reflectMode() throws Exception {System.out.println("============================================================");System.out.println("通過反射方式實例化對象");Class[] parameterTypes = new Class[] {Integer.class, String.class};Constructor constructor = Book.class.getConstructor(parameterTypes);Book book = (Book) constructor.newInstance(3, "大道揚帆");return book; }// 3-1.通過反射方式實例化對象還有一種方式，但本質上其實和上面的一樣,但需要類本身有無參構造函數 public static Book reflectAnotherMode() throws Exception {System.out.println("============================================================");System.out.println("通過反射方式實例化對象的另外一種方式");Book book = (Book) Class.forName("instantiation.Book").newInstance();return book; }// 4.調用已存在對象的clone()方法實例化對象 public static Book cloneMode(Book book) throws Exception {System.out.println("============================================================");System.out.println("調用已存在對象的clone()方法實例化對象");Book newBook = (Book) book.clone();System.out.println("原對象和克隆對象是同一個對象嗎？" + (book == newBook));return newBook; }// 5.對象序列化后可以通過反序列化創建對象 public static Book unSerializedMode() throws Exception {System.out.println("============================================================");System.out.println("對象序列化后可以通過反序列化創建對象");Book book = new Book(5, "大道揚帆");ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(new File("D:/book.obj")));objectOutputStream.writeObject(book);ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream(new File("D:/book.obj")));Book newBook = (Book) objectInputStream.readObject();System.out.println("原對象和反序列化的對象是同一個嗎？" + (book == newBook));return newBook; }public static void main(String[] args) throws Exception {System.out.println(Instantiation.newMode());System.out.println(Instantiation.factoryMode());System.out.println(Instantiation.reflectMode());System.out.println(Instantiation.reflectAnotherMode());Book book = new Book(4, "大道揚帆");System.out.println(Instantiation.cloneMode(book));System.out.println(Instantiation.unSerializedMode()); }

}

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轉載于:https://blog.51cto.com/13855604/2170171

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