重载和重写的区别

重载：
1、

public class TestOverLoad {
	public static void main(String[] args) {
		Person p = new Person();
		Person p1 = new Person(400);
		Person p2 = new Person(2, 500);
		p.info();
		p.info("ok");
	}
}

class Person {

	Person() {
		id = 0;
		age = 20;
	}

	Person(int _id) {
		id = _id;
		age = 23;
	}

	Person(int _id, int _age) {
		id = _id;
		age = _age;
	}

  //成员变量定义
  private int id;
  private int age = 20;
  //方法定义
  public int getAge() {return age;}
  public void setAge(int i) {age = i;}
  public int getId() {return id;}

  void info() {
  	System.out.println("my id is : " + id);
  }

  void info(String t) {
  	System.out.println(t + " id " + id);
  }
}

public class Test {
	void max(int a , int b) {
		System.out.println( a > b ? a : b );
	}

	void max(short a , short b) {
		System.out.println("short");
		System.out.println( a > b ? a : b );
	}

	void max(float a, float b) {
		System.out.println( a > b ? a : b );
	}

	public static void main(String[] args) {
		Test t = new Test();
		t.max(3, 4);
		short a = 3;
		short b = 4;
		t.max(a, b);
	}
}

重写：

class Person {
    private String name;
    private int age;
    public void setName(String name){this.name=name;}
    public void setAge(int age) {this.age=age;}
    public String getName(){return name;}
    public int getAge(){return age;}
    public String getInfo() {
          return "Name: "+ name + "\n" +"age: "+ age;
  }
}

class Student extends Person {
    private String school;
    public String getSchool() {return school;}
    public void setSchool(String school)
    {this.school =school;}
    public String getInfo() {
      return  "Name: "+ getName() + "\nage: "+ getAge() 
                    + "\nschool: "+ school;
		}
}

public class TestOverWrite {
public static void main(String arg[]){
        Student student = new Student();
        Person person = new Person();
        person.setName("none");
        person.setAge(1000);
        student.setName("John");    
        student.setAge(18);
        student.setSchool("SCH");
        System.out.println(person.getInfo());
        System.out.println(student.getInfo());
    }
}