先创建一个Point类，然后定义Trianglele类。

在Trianglele类中定义三个Point的实体来表示一个三角形的三个点，再定义构造方法对这三个点进行初始化，然后定义两个方法求三角形的周长、面积。

定义一个测试类，在main()中创建一个对象，求给定三点的三角形的周长、面积。

package test1;
import java.util.*;

public class Main {
	public static void main(String args[]) 
	{
		Scanner sc = new Scanner(System.in);
		Point p1 = new Point(0, 0);
		Point p2 = new Point(3, 0);
		Point p3 = new Point(0, 4);
		Trianglele t1 = new Trianglele(p1, p2, p3);
		System.out.println("三角形的面积：" + t1.getArea());
		System.out.println("三角形的周长：" + t1.getPerimeter());
		sc.close();
	}
}
class Point
{
	double x, y;
	public Point(double x, double y)
	{
		this.x = x;
		this.y = y;
	}
}
class Trianglele
{
	private Point point1, point2, point3;
	private double a, b, c;
	public Trianglele(Point point1, Point point2, Point point3)
	{
		this.point1 = point1;
		this.point2 = point2;
		this.point3 = point3;
	}
	private void getSideLength()
	{//求三边边长
		a = Math.sqrt(Math.pow((point2.x - point1.x), 2) + Math.pow((point2.y - point1.y), 2));
		b = Math.sqrt(Math.pow((point3.x - point2.x), 2) + Math.pow((point3.y - point2.y), 2));
		c = Math.sqrt(Math.pow((point3.x - point1.x), 2) + Math.pow((point3.y - point1.y), 2));
	}
	public double getArea()
	{
		getSideLength();
		double p = (a + b + c) / 2.0;
		return Math.sqrt(p * (p-a)* (p-b) * (p-c));
	}
	public double getPerimeter()
	{
		return a + b + c;
	}
}