constructdemo.java

Java语言是目前最流行

//构造方法的重载
class RunDemo
{
	private String userName,password;
	
	RunDemo()
	{
		System.out.println("All is null");	
	}	
	RunDemo(String name)
	{
		userName=name;	
	}
	RunDemo(String name,String pwd)
	{
		this(name);
		password=pwd;
		check();	
	}
	void check()
	{
		String s=null;
		if (userName!=null)
			s="userName:"+userName;
		else
			s="please input your password!";	
		if (password!="ThisWord")
			s=s+" invaid!";
		else
			s=s+"  password:*******";
			System.out.println(s);
	}
}
class Demo
{
	public static void main(String[] aa)
	{
		new RunDemo();
		new RunDemo("Bill");
		new RunDemo(null,"Bill");
		new RunDemo("Bill","ThisWord");			
	}	
}