A227A/D242: 3D Environments in Java a

Quiz 1.

Name: ____________________________________________________

1. Suppose we have a class called MyChild. MyChild has a method called gotoSchool().

Fill in the code for the method gotoSchool (below) that will make all children go to school.

class MyMother {

MyChild[] children;

//***** Contructor

public MyMother(){

children = new MyChild[4];

for(int i=0; i<children.length; i++)

children[i] = new MyChild();

}

//*********************

public void gotoSchool(){

for(int i=0; i<children.length; i++)

children[i]. gotoSchool();

}

}

2. Rewrite the following code to make it faster:

for(int i=0; i<100; i++){

double ang = Math.PI/180.*30.;

double d = Math.cos(Math.PI/180.*i) * Math.sin(ang);

}

double ang = Math.PI/180.*30.;

sinang = Math.sin(ang);

double d;

double div = Math.PI/180.;

for(int i=0; i<100; i++){

d = Math.cos(div*i) * sinang;

}

3. Draw the result of this code:

//********************

public void draw(Graphics g){

Polygon poly = new Polygon();

poly.addPoint(0, 0);

poly.addPoint(0, 100);

poly.addPoint(100, 100);

g.drawPolygon(poly);

}

4. Can we write a DXF file from an applet? (Explain why or why not)

No, because the browser will throw a security exception.

5. Write the code that would reverse the order of an array of points[] (that is, the first to become the last, the second to become the last-1, etc.).

// Make a copy of points array

MyPoint[] copy;

copy = new MyPoint[points.length];

// Reverse the points

for(int j=0; j<points.length; j++)

copy[points.length -1-j] = new MyPoint(points[j].x, points[j].y, points[j].z);

// Copy back to points

for(int j=0; j<points.length; j++)

points[j] = new MyPoint(copy[j].x, copy[j].y, copy[j].z);