先创建一个Point类，然后定义Triangle类。在Triangle类中定义3个Point的对象用来表示一个三角形的三个点，再定义一个方法setTri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。在main()中创建一个三角形对象，求给定三点的三角形的周长、面积。将setTri改用构造方法实现初始化用java编译

好的，我明白了。以下是Java代码实现：

Point类：

public class Point {
    private double x;
    private double y;

    public Point(double x, double y) {
        this.x = x;
        this.y = y;
    }

    public double getX() {
        return x;
    }

    public double getY() {
        return y;
    }

    public double distance(Point other) {
        double dx = x - other.getX();
        double dy = y - other.getY();
        return Math.sqrt(dx * dx + dy * dy);
    }
}

Triangle类：

public class Triangle {
    private Point p1;
    private Point p2;
    private Point p3;

    public Triangle(Point p1, Point p2, Point p3) {
        this.p1 = p1;
        this.p2 = p2;
        this.p3 = p3;
    }

    public double getPerimeter() {
        double side1 = p1.distance(p2);
        double side2 = p2.distance(p3);
        double side3 = p3.distance(p1);
        return side1 + side2 + side3;
    }

    public double getArea() {
        double side1 = p1.distance(p2);
        double side2 = p2.distance(p3);
        double side3 = p3.distance(p1);
        double s = (side1 + side2 + side3) / 2;
        return Math.sqrt(s * (s - side1) * (s - side2) * (s - side3));
    }

    public void setTri(Point p1, Point p2, Point p3) {
        this.p1 = p1;
        this.p2 = p2;
        this.p3 = p3;
    }
}

在main()方法中创建对象并计算周长和面积：

public static void main(String[] args) {
    Point p1 = new Point(0, 0);
    Point p2 = new Point(3, 0);
    Point p3 = new Point(0, 4);
    Triangle t = new Triangle(p1, p2, p3);
    System.out.println("周长是：" + t.getPerimeter());
    System.out.println("面积是：" + t.getArea());
}

输出结果：

周长是：12.0
面积是：6.0