String str = new String("str");
2.通过Java的反射机制
public static void main(String[] args) throws Exception {
// 获取类的Class对象
String str = (String)Class.forName("java.lang.String").newInstance();
System.out.println(str); }
3.通过clone机制(克隆机制)
=========================Myclass.java===========================================public class MyClass implements Cloneable {
private int value;
public MyClass(int value) {
this.value = value;
}
public int getValue() {
return value;
}
@Override
public MyClass clone() throws CloneNotSupportedException {
return (MyClass) super.clone();
}
}
===========================Main.java=============================================
public class Main {
public static void main(String[] args) throws CloneNotSupportedException {
MyClass obj1 = new MyClass(10);
MyClass obj2 = obj1.clone();
System.out.println(obj1.getValue()); // 输出：10
System.out.println(obj2.getValue()); // 输出：10
}
}
4.通过序列化机制
通过序列化机制来创建新的对象。序列化是将对象转换为字节流的过程，以便可以将其存储在磁盘上或通过网络传输。反序列化则是将字节流转换回对象的过程。
===================================================================================================
import java.io.*;
public class MyClass implements Serializable {
private int value;
public MyClass(int value) {
this.value = value;
}
public int getValue() {
return value;
}
private void writeObject(ObjectOutputStream out) throws IOException {
out.writeInt(value * 2);
}
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
value = in.readInt();
}
}
===================================================================================================
public class Main {
public static void main(String[] args) throws IOException, ClassNotFoundException {
MyClass obj1 = new MyClass(10);
FileOutputStream fileOut = new FileOutputStream("obj1.ser");
ObjectOutputStream out = new ObjectOutputStream(fileOut);
out.writeObject(obj1);
out.close();
fileOut.close();
FileInputStream fileIn = new FileInputStream("obj1.ser");
ObjectInputStream in = new ObjectInputStream(fileIn);
MyClass obj2 = (MyClass) in.readObject();
in.close();
fileIn.close();
System.out.println(obj1.getValue()); // 输出：10
System.out.println(obj2.getValue()); // 输出：20
}
}
5、构造函数对象的newInstance()方法
类Constructor也有newInstance方法，这一点和Class有点像。从它的名字可以看出它与Class的不同，Class是通过类来创建对象，而Constructor则是通过构造器。依然使用第一个例子中的Test类。
public static void main(String[] args) throws Exception {
Constructor
try {
constructor = Test.class.getConstructor();
Test t = constructor.newInstance();
} catch (InstantiationException |
IllegalAccessException |
IllegalArgumentException |
InvocationTargetException |
NoSuchMethodException |
SecurityException e) {
e.printStackTrace();
}
}