Transcript Nested `for` loops

Nested for Loops
Derived from Building Java Programs
by Stuart Reges & Marty Stepp
Example output to produce: hourglass
+------+
|\
/|
| \ / |
| \/ |
| /\ |
| / \ |
|/
\|
+------+
Hourglass: Decomposition
+------+
|\
/|
| \ / |
| \/ |
| /\ |
| / \ |
|/
\|
+------+
Hourglass: Pseudocode
+------+
|\
/|
| \ / |
| \/ |
| /\ |
| / \ |
|/
\|
+------+
draw line
draw top half
draw bottom half
draw line
Hourglass: Pseudo Code
•
•
•
•
Draw a solid line
Draw the top half of the hourglass
Draw the bottom half of the hourglass
Draw a solid line
main( ) looks like
public class DrawFigure {
public static void main (String [] args) {
drawLine();
drawTop ();
drawBottom ();
drawLine ();
}
public static void drawLine () {
code
}
SOLVE EACH METHOD INDEPENDENTLY
Solve for the solid line
•
•
•
•
Write a + on the output line
Write 6 – on the output line
Write a + on the output line
Go to a new output line
public static void drawLine( ) {
System.out.print ("+");
for (int i=1; i <= 6; i++) {
System.out.print (“-”);
}
System.out.println (“+”);
}
Translated into
a static method
Solve for Top Half of Hourglass
for (each of 3 lines) {
write a bar on the output line.
write some spaces on the output line.
write a backslash on the output line.
write some spaces on the output line.
write a slash on the output line.
write some spaces on the output line.
write a bar on the output line.
go to a new line of output.
}
To help you… create a table to determine the output of
spaces
Table for Top Half of hourglass
Line
Spaces
Spaces
Spaces
1
0
4
0
2
1
2
1
3
2
0
2
Refining pseudocode for Top Half of Hourglass
for (line going from 1 to 3) {
write a bar on the output line.
write (line – 1) spaces on the output line.
write a backslash on the output line.
write (6 - 2 * line) spaces on the output line.
write a slash on the output line.
write (line – 1) spaces on the output line.
write a bar on the output line.
go to a new line of output.
}
drawTop ()
// produces the top half of the hourglass figure
public class drawTop {
for (int line = 1; line <= 3; line++) {
System.out.print (“|”);
for (int i = 1; i <= (line-1); i++) {
system.out.print(“ “);
}
System.out.print (“\\”);
for (int i = 1; i <= (6-2*line); i++) {
system.out.print(“ “);
}
System.out.print (“/”);
for (int i = 1; i <= (line-1); i++) {
system.out.print(“ “);
}
System.out.print (“|”);
}
}
Using a Class Constant
// refers to height of two halves
public static final int SUB_HEIGHT = 3;
public static void drawLine( ) {
System.out.print ("+");
for (int i=1; i <= (2*SUB_HEIGHT); i++) {
System.out.print (“-”);
}
System.out.println (“+”);
}
drawTop ( ) using constant
// produces the top half of the hourglass figure
public class drawTop {
for (int line = 1; line <= SUB_HEIGHT; line++) {
System.out.print (“|”);
for (int i = 1; i <= (line-1); i++) {
system.out.print(“ “);
}
System.out.print (“\\”);
for (int i = 1; i <= ((2*SUB_HEIGHT)-2*line); i++) {
system.out.print(“ “);
}
System.out.print (“/”);
for (int i = 1; i <= (line-1); i++) {
system.out.print(“ “);
}
System.out.print (“|”);
}
}
Rocket: Assignment #3
/**\
//**\\
///**\\\
////**\\\\
/////**\\\\\
+=*=*=*=*=*=*+
|../\..../\..|
|./\/\../\/\.|
|/\/\/\/\/\/\|
|\/\/\/\/\/\/|
|.\/\/..\/\/.|
|..\/....\/..|
+=*=*=*=*=*=*+
|\/\/\/\/\/\/|
|.\/\/..\/\/.|
|..\/....\/..|
|../\..../\..|
|./\/\../\/\.|
|/\/\/\/\/\/\|
+=*=*=*=*=*=*+
/**\
//**\\
///**\\\
////**\\\\
/////**\\\\\
Write a java program
to produce this output.
The height is 3; allow
for the height to vary
(with multiples of 3).
Rocket: Assignment #3 Decomposition
/**\
//**\\
///**\\\
////**\\\\
/////**\\\\\
+=*=*=*=*=*=*+
|../\..../\..|
|./\/\../\/\.|
|/\/\/\/\/\/\|
|\/\/\/\/\/\/|
|.\/\/..\/\/.|
|..\/....\/..|
+=*=*=*=*=*=*+
|\/\/\/\/\/\/|
|.\/\/..\/\/.|
|..\/....\/..|
|../\..../\..|
|./\/\../\/\.|
|/\/\/\/\/\/\|
+=*=*=*=*=*=*+
/**\
//**\\
///**\\\
////**\\\\
/////**\\\\\
Rocket: Assignment #3 pseudocode
/**\
//**\\
///**\\\
////**\\\\
/////**\\\\\
+=*=*=*=*=*=*+
|../\..../\..|
|./\/\../\/\.|
|/\/\/\/\/\/\|
|\/\/\/\/\/\/|
|.\/\/..\/\/.|
|..\/....\/..|
+=*=*=*=*=*=*+
|\/\/\/\/\/\/|
|.\/\/..\/\/.|
|..\/....\/..|
|../\..../\..|
|./\/\../\/\.|
|/\/\/\/\/\/\|
+=*=*=*=*=*=*+
/**\
//**\\
///**\\\
////**\\\\
/////**\\\\\
drawCone ( );
drawLine ( );
drawM ( );
drawW ( );
drawLine ( );
drawW ( );
drawM ( );
drawLine ( );
drawCone ( );
In-Class Exercise
• Create pseudocode for drawCone( );
• Create output table for drawCone( );
• Write code for drawCone( );
Note:
Use a constant for HEIGHT.
Compute height and length based on HEIGHT.
Note:
Top of rocket and booster of rocket are the same shape.