Q:

How can I get the different results as I put the number?

I wanna get the different results as the inputted number.
For example, when I put 4 I get the results of the rectangle and when I put 3 I get the triangle.
import java.util.Scanner;

public class Source9_1 {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int x, y; // 클래스 Parameter(내부 변수)

    Point[] v = new Point[n]

    for(int i=0; i <= v.length; i++) {
        v[i] = new Point();
        v[i].

    }
}

class Point {
    int x, y; // 클래스 Parameter (내부 변수)

    public void setPoint(int x, int y) { // Point 세팅
        this.x = x;
        this.y = y;
    }

    public void printPoint() { // Point 출력
        System.out.println("x = " + x + ", y = " + y);
    }
}

class Rectangle extends Point {
    Point[] p = new Point[4];

    Rectangle(Point[] p) {
        this.p = p;
    }
}

class Triangle extends Point {
    Point[] p = new Point[3]; // 3개의 Point인스턴스를 담을 배열 생성

    Triangle(Point[] p) {
        this.p = p;
    }
}

class Shape extends Point { // Point 배열 및 상속을 받아 세팅 후 출력가능한 클래스
    Point coord[10];
    static int s = 0; // 불릴 때마다 값 증가 ???

    public void printShapePoint() { // 배열에 담은 Point 출력

    }

    public void setShapePoint() { // 배열에 담기 위해 Point 증가

    }
}

So far, I coded like this but I don't know what to do now.
How can I get the different result as I put the number?
This is the result what I want

A:

First of all, about your Rectangle and Triangle classes. I feel like you have missed your point there (pun not intended), because you've put both extending the Point class. That doesn't make much sense, since you have the Shape class, which would do a much better job as the superclass for them.
So:
class Rectangle extends Shape {
    ...
}

class Triangle extends Shape {
    ...
}

With that out of the way, what you have so far:

You are capturing the number of points from the input;
You are creating an array of that size;
You are instantiating and setting an Point object for each of the array positions.

What you need to do next:

Capture the points coordinates from the input
Set said coordinates to the Point objects
Instantiate an Triangle or Rectangle object, depending on how many points you have.

So, inside your for statement you will want to do:
for (int i=0; i <= v.length; i++) {
    v[i] = new Point();
    x = sc.nextInt(); // Save 'x' value into the variable
    y = sc.nextInt(); // Save 'y' value into the variable
    v[i].setPoint(x, y); // Set both values using the method from Point
}

Then, since both Rectangle and Triangle have Shape as a common superclass, you are allowed to put objects of either one of these class in a Shape variable. So right after the for statement you will want to do:
Shape s; // Create the empty variable here, so it will exist outside the if-else scope
if (n == 3)
    s = new Triangle(v);
else
    s = new Rectangle(v);

Finally, just print your points:
for (int i = 0; i < v.length; i++)
    v[i].printPoint();

And that's pretty much it.

