第一种:方法重载(赋初始值)People类:
public class People{
	protected String name;
	protected int stuNo;
	protected int age;
	protected String picName;
	
	//方法重载
	protected void say(String _n){
		this.name=_n;
	};
	protected void say(String _n,int _sn){
		this.name=_n;
		this.stuNo=_sn;
	};
	protected void say(String _n,int _sn,int _a){
		this.name=_n;
		this.stuNo=_sn;
		this.age=_a;
	};
	protected void say(String _n,int _sn,int _a,String _pn){
		this.name=_n;
		this.stuNo=_sn;
		this.age=_a;
		this.picName=_pn;
	};
}  
测试: MainDao类
	public static void main(String[] args) {
		People p=new People();
		p.say("张一");
		printSay(p);
		
		p.say("张二", 12020401);
		printSay(p);
		
		p.say("张三", 12020402, 23);
		printSay(p);
		
		p.say("张四", 12020403, 25, "时光与你");
		printSay(p);
	};
	
	public static void printSay(People p){
		System.out.println(p.name);
		System.out.println(p.stuNo);
		System.out.println(p.age);
		System.out.println(p.picName);
	}; 
第二种:构造重载(赋初始值)Student类:
public class Student {
	protected String name;
	protected int stuNo;//学号
	protected int age;
	protected String picName;//呢称
	
	//构造重载
	public Student(){
		
	};
	public Student(String n){
		this.name=n;
	};
	public Student(String n,int sn){
		this.name=n;
		this.stuNo=sn;
	};
	public Student(String n,int sn,int a){
		this.name=n;
		this.stuNo=sn;
		this.age=a;
	};
	public Student(String n,int sn,int a,String pn){
		this.name=n;
		this.stuNo=sn;
		this.age=a;
		this.picName=pn;
	}
}
测试:MainDao类
	public static void main(String[] args) {
		Student s=new Student();
		printStudent(s);
		
		Student s1=new Student("张一");
		printStudent(s1);
		
		Student s2=new Student("张二",121101);
		printStudent(s2);
		
		Student s3=new Student("张三",121102,23);
		printStudent(s3);
		
		Student s4=new Student("张四",121103,25,"时光与你");
		printStudent(s4);
		
	}
	public static void printStudent(Student sdt){
		System.out.println(sdt.name);
		System.out.println(sdt.stuNo);
		System.out.println(sdt.age);
		System.out.println(sdt.picName);
		System.out.println("-----------分割线------------");
	};