There is no direct method to draw a triangle.
You can use drawPolygon() method for this.
It takes three parameters in the following form:
drawPolygon(int x[],int y[], int number_of_points);
To draw a triangle:
(Specify the x coordinates in array x and y coordinates in array y and number of points which will be equal to the elements of both the arrays.Like in triangle you will have 3 x coordinates and 3 y coordinates which means you have 3 points in total.)
Suppose you want to draw the triangle using the following points:(100,50),(70,100),(130,100)
Do the following inside public void paint(Graphics g):
int x[]={100,70,130};
int y[]={50,100,100};
g.drawPolygon(x,y,3);
Similarly you can draw any shape using as many points as you want.