public Student(int age){
    super();
    this.age = age;
}
 
public Student(String name , int age){
    /*
        super(); 注意，這里不能再調(diào)用super();因為下邊的this(age);調(diào)用了上方的構(gòu)造器，已經(jīng)存在了    
        super();該構(gòu)造器內(nèi)不能再次調(diào)用。所以只寫一個this(age)就夠了;
    */
    this(age);
    this.name = name;
}

public class Puppy{
  public Puppy( ) { }
  public Puppy(String name) {

       //這個構(gòu)造器僅有一個name

      }
}  

public class Dog{
 
    /**
     * 帶參構(gòu)造函數(shù)
     * @param name
     * @param age
     */
    public Dog(String name,int age){
        this.age = age;
        this.name = name;
    }
 
    /**
     * 無慘構(gòu)造函數(shù)
     */
    public Dog(){}
 
    String name;
    int age;
 
    public void ptint(){
        System.out.println("name = "+this.name+";age = "+age);
    }
 
    public static void main(String[] args) {
        new Dog().ptint();
        new Dog("花花",9).ptint();
    }
}

Puppy p = new Puppy( )；
Puppy p1 = new Puppy(“張三”）；

class Triangle
{
int x,y,z;
public Triangle(int i,int j,int k)
{  
x=i;y=j;z=k;
public static bpplean judge(Triangle m)
{ 
 if(Math.sqrt(m.x*m.x+m.y*m.y)= =Math.sqrt(m.z*m.z))
    //引用Math類庫的sqrt()方法
    return true;
    else
    return false;
}
public static void main(String args[]) {
Triangle t1=new Triangle(3,4,5);
if(judge(t1))   //調(diào)用judge()方法，判斷t1的成員變量是
    //否能構(gòu)成直角三角形的3條邊長
System.out.println("這是一個直角三角形");
else
System.out.Println("這不是一個直角三角形");
}
 
}