chapter 11 slides

// Java1101.java// This program demonstrates using multiple variables in a <for> loop.

public class Java1101{

public static void main(String args[]){

int p, q;for (p=1, q=5; p <= 5; p++,q--)

System.out.println("p = " + p + " q = " + q);}

} Java1101.java Output

p = 1 q = 5p = 2 q = 4p = 3 q = 3p = 4 q = 2p = 5 q = 1

// Java1102.java// This program demonstrates a practical example of using multiple// variables in a <for> loop. This program counts the number of// quarters, as well as the value of the quarters.



int count;double value;for (count = 1, value = 0.25; count <= 20; count++, value+=0.25)

System.out.println(count + " Quarter(s) equals " + value);}

}

Java1102.java Output

1 Quarter(s) equals 0.252 Quarter(s) equals 0.53 Quarter(s) equals 0.754 Quarter(s) equals 1.05 Quarter(s) equals 1.256 Quarter(s) equals 1.57 Quarter(s) equals 1.758 Quarter(s) equals 2.09 Quarter(s) equals 2.2510 Quarter(s) equals 2.511 Quarter(s) equals 2.7512 Quarter(s) equals 3.013 Quarter(s) equals 3.2514 Quarter(s) equals 3.515 Quarter(s) equals 3.7516 Quarter(s) equals 4.017 Quarter(s) equals 4.2518 Quarter(s) equals 4.519 Quarter(s) equals 4.7520 Quarter(s) equals 5.0

// Java1103.java// This program introduces text window input using the // InputStreamReader class found in the java.io package.import java.io.*; // Line 1public class Java1103{

public static void main (String args[]) throws IOException // Line 2{

BufferedReader input = new BufferedReader(new InputStreamReader(System.in)); // Line 3

String name;int age;double gpa;

System.out.print("Enter Name ===>> "); // Line 4name = input.readLine(); // Line 5

System.out.print("Enter Age ===>> ");age = Integer.parseInt(input.readLine()); // Line 6

System.out.print("Enter GPA ===>> ");gpa = Double.parseDouble(input.readLine()); // Line 7

System.out.println();System.out.println("Name: " + name);System.out.println("Age: " + age);System.out.println("GPA: " + gpa);

}}


Enter Name ===>> Isolde EchleEnter Age ===>> 29Enter GPA ===>> 3.785

Name: Isolde EchleAge: 29GPA: 3.785

Keyboard Text Window Input

import java.io.*;// Line 1

public class Java1103{ public static void main (String args[]) throws IOException // Line 2 { BufferedReader input = new BufferedReader(new InputStreamReader(System.in)); // Line 3 String name; int age; double gpa; System.out.print("Enter Name ===>> "); // Line 4 name = input.readLine(); // Line 5 System.out.print("Enter Age ===>> "); age = Integer.parseInt(input.readLine()); // Line 6 System.out.print("Enter GPA ===>> "); gpa = Double.parseDouble(input.readLine()); // Line 7

Keyboard Text Input Line 1

import java.io.*;

This import statement gives access to the input/output classes of the java.io package.


public static void main (String args[ ]) throws IOException

The statement throws IOException alerts Java of possible errors. Specifically errors during input and output, which need to be ignored or thrown away.


BufferedReader input = new BufferedReader(new InputStreamReader(System.in));

This statement constructs the object input of the BufferedReader class. input will be in charge of handling the data that users enter at the keyboard during program execution.


System.out.print("Enter Name ===>> ");

This statement provides a prompt for the program user prior to the statement that expects user keyboard input.


Name = input.readLine();

input is an object of the BufferedReader class. readLine is one of its methods. This statement stops program execution and waits for user input from the keyboard.


System.out.print("Enter Age ===>> ");age = Integer.parseInt(input.readLine());

The input.readLine statement is used to stop program execution and wait for user input. This time the statement is more complex. Numeric input is requested and readLine can only digest string input. Recall that Integer.parseInt can convert string data to numeric Integer data.


System.out.print("Enter GPA ===>> ");gpa = Double.parseDouble(input.readLine());

Line 7 presents nothing new. This is now a repetition of the keyboard prompt followed by keyboard input that is converted. In this case the string input is converted to a Double type.

#1 Start by adding the Input/Output Java package:Import java.io.*;

#2 Alter the main method method by usingpublic static void main (String args[]) throws IOException

#3 Define a BufferedReader object for program inputBufferedReader input =

new BufferedReader(newInputStreamReader(System.in));

#4 Provide a user prompt likeSystem.out.print("Enter Age ===>> ");

#5 Get user input and convert string input if necessary:age = Integer.parseInt(input.readLine());

Keyboard Text Input Summary

The for loop is ideal for loop structures that repeat some process a known - or fixed - number of times.

When to Use the <for> Loop

The while loop structure needs to be used when a condition must be checked before even a single loopbody is executed.

When to Use the <while> Loop

The do..while loop structure needs to be used when the loop body must be executed at least once.

When to Use the <do..while> Loop

Program loop structures frequently use variables that sum-up entered values. Such a variable is called an accumulator.

Make sure that the accumulator is initialized before it is used inside the loop structure.

This is one of many reasons why OOP adds reliability to programming. The use of classes with constructors can insure that all data fields in an object are properly initialized when a new object of a class is instantiated.

Initialize Your Accumulators

// Java1104.java// This program computes the average for a fixed set of grades using a for loop. import java.io.*;public class Java1104{

public static void main (String args[]) throws IOException{

BufferedReader input = new BufferedReader(new InputStreamReader(System.in)); int k; // loop counter

int count; // quantity of entered gradesint grade; // individually entered gradeint sum = 0; // sum of entered gradesdouble mean; // average of entered gradesSystem.out.print("Enter grade count ===>> ");count = Integer.parseInt(input.readLine());for (k = 1; k <= count; k++){

System.out.print("Enter grade ===>> ");grade = Integer.parseInt(input.readLine());sum += grade;

}mean = (double) sum / count;System.out.println("Average Grade: " + mean);

}}


How many grades will be averaged ===>> 5Enter grade ===>> 60Enter grade ===>> 70Enter grade ===>> 80Enter grade ===>> 90Enter grade ===>> 100

Grade average: 80

// Java1105.java// This program computes the average for an unknown quantity of// grades using a while loop. This example produces a logic error, which// is best seen by entering the same set of numbers.import java.io.*;public class Java1105{


BufferedReader input = new BufferedReader(new InputStreamReader(System.in));int count = 0; // quantity of entered gradesint grade = 0; // individually entered gradeint sum = 0; // sum of entered gradesdouble mean; // average of entered grades

while (grade != -999){

System.out.print("Enter grade ===>> ");grade = Integer.parseInt(input.readLine());count++;sum += grade;

}

System.out.println();mean = (double) sum / count;System.out.println("Average Grade: " + mean);

}}


Enter grade ===>> 100Enter grade ===>> 100Enter grade ===>> 100Enter grade ===>> 100Enter grade ===>> 100Enter grade ===>> -999

Average Grade: -83.16666666666667

// Java1106.java// This program computes the average for an unknown quantity of grades using a while loop, and fixes the // logic problem of the previous program example with a conditional statement.import java.io.*;public class Java1106{


BufferedReader input = new BufferedReader(new InputStreamReader(System.in)); int count = 0; // quantity of entered grades

int grade = 0; // individually entered gradeint sum = 0; // sum of entered gradesdouble mean; // average of entered gradeswhile (grade != -999){

System.out.print("Enter grade ===>> ");grade = Integer.parseInt(input.readLine());if (grade != -999){

count++; // counter sum += grade; // accumulator

}} System.out.println();mean = (double) sum / count;System.out.println("Average Grade: " + mean);

}}



Average Grade: 100.0

// Java1107.java// This program computes the average with a do..while loop.import java.io.*;public class Java1107{


BufferedReader input = new BufferedReader(new InputStreamReader(System.in)); int count = 0; // quantity of entered grades

int grade = 0; // individually entered gradeint sum = 0; // sum of entered gradesdouble mean; // average of entered gradesdo {

System.out.print("Enter grade ===>> ");grade = Integer.parseInt(input.readLine());if (grade != -999){

count++; // counter sum += grade; // accumulator

}} while (grade != -999); System.out.println();mean = (double) sum / count;System.out.println("Average Grade: " + mean);

}}



Grade average: 80

The while loop and do...while loop are ideally used for repetition that depends on a certain condition to be true.This is not necessarily a counting condition. The loop may exit when a certain value is entered and the loop condition becomes true.

Flag is the term used in computer science to detect if a certain value is entered or altered to change the loop exit condition. The value that is entered or altered is called the Flag.

<while> and <do..while> Need a Flag

// Java1108.java// This program demonstrates nested one-way selection.import java.io.*;



BufferedReader input = new BufferedReader(new InputStreamReader(System.in));double bonus = 500; // year-end employee bonusdouble sales; // yearly salesint years; // years worked with company

System.out.print("Enter yearly sales ===>> ");sales = Double.parseDouble(input.readLine()); if (sales >= 250000){

System.out.println("Your bonus will be increased by $1000.00"); bonus += 1000;System.out.print("Enter years worked with the company ===>> ");years = Integer.parseInt(input.readLine());if (years > 10){

System.out.println("Your bonus will be increased by $250.00");bonus += 250;

}}System.out.println();System.out.println("Your year-end bonus will be: $" + bonus);

}}

Java1108.java Output #1

Enter your yearly sales ===>> 300000

Your bonus will be increased by $1000.00Enter years worked with the company ===>> 15Your bonus will be increased by $250.00

Your year-end bonus will be: 1750



Your bonus will be increased by $1000.00Enter years worked with the company ===>> 5





// Java1109.java// This program displays an admission message based on an entered// SAT score. It also determines financial need with a nested if...else structure.

import java.io.*;



BufferedReader input = new BufferedReader(new InputStreamReader(System.in));int sat;double income;System.out.print("Enter your SAT score ===>> ");sat = Integer.parseInt(input.readLine());if (sat >= 1100){

System.out.println("You are admitted");System.out.print("Enter your family income ===>> ");income = Double.parseDouble(input.readLine());if (income <= 20000)

System.out.println("You will receive financial aid");else

System.out.println("You will not receive financial aid");}else{

System.out.println("You are not admitted");}

}}


Enter your SAT score ===>> 1500

You are admitted

Enter your family income ===>> 10000

You will receive financial aid



You are admitted

Enter your family income ===>> 75000

You will not receive financial aid



You are not admitted

// Java1110.java// This program assigns grades 'A'..'F' based on numerical scores using multiple nested if..else statements.

import java.io.*;



BufferedReader input = new BufferedReader(new InputStreamReader(System.in));double score;char grade;

System.out.print("Enter your numerical score ===>> ");score = Double.parseDouble(input.readLine());if (score >= 90.0)

grade = 'A';else if (score >= 80.0)

grade = 'B';else if (score >= 70.0)

grade = 'C';else if (score >= 60.0)

grade = 'D';else

grade = 'F';

System.out.println("Your grade will be: " + grade); }

}


Enter your numerical score ===>> 100Your grade will be: A


Enter your numerical score ===>> 90.5Your grade will be: A


Enter your numerical score ===>> 83.756Your grade will be: B


Enter your numerical score ===>> 79.999Your grade will be: C


Enter your numerical score ===>> 60Your grade will be: D


Enter your numerical score ===>> 59.999Your grade will be: F

Output for Java1111.java, Java1112.java and Java1113.java

1 * 11 = 112 * 11 = 223 * 11 = 334 * 11 = 445 * 11 = 55

1 * 12 = 122 * 12 = 243 * 12 = 364 * 12 = 485 * 12 = 60

1 * 13 = 132 * 13 = 263 * 13 = 394 * 13 = 525 * 13 = 65

// Java1111.java// This program displays several multiplication tables using// nested <for> loop structures.



for (int table = 11; table <= 13; table++){

for (int k = 1; k <= 5; k++){

System.out.println(k + " * " + table + " = " + k * table);}System.out.println();

}}

}

// Java1112.java// This program displays several multiplication tables using// nested pre-condition <while> loop structures.public class Java1112{


int k = 1;int table = 11;while (table <= 13){

while (k <= 5){

System.out.println(k + " * " + table + " = " + k * table);k++;

}System.out.println();k = 1;table++;

}}

}

// Java1113.java// This program displays several multiplication tables using// nested post-condition <do..while> loop structures.



int k = 1;int table = 11;do {

do{

System.out.println(k + " * " + table + " = " + k * table);k++;

}while (k <= 5);System.out.println();k = 1;table++;

}while (table <= 13);

}}

The program style of control structures varies considerably. Two different styles will be shown here with <do...while>, which shows a general pattern of choosing more clarity or choosing less space.

Control Structure Style

do { do { System.out.println(k + " * " + table + " = " + k * table); k++; } while (k <= 5); System.out.println(); k = 1; table++;}while (table <= 13);

Style 1

do { do { System.out.println(k + " * " + table + " = " + k * table); k++; } while (k <= 5); System.out.println(); k = 1; table++;} while (table <= 13);

Style 2

// Java1114.java// This program demonstrates compound decisions with the logical or ( || ) operator.

import java.io.*;



BufferedReader input = new BufferedReader(new InputStreamReader(System.in));int education; // years of educationint experience; // years of work experience

System.out.print("Enter years of education ===>> ");education = Integer.parseInt(input.readLine());System.out.print("Enter years of experience ===>> ");experience = Integer.parseInt(input.readLine());

if ((education >= 16) || (experience >= 5))System.out.println("You are hired");

elseSystem.out.println("You are not qualified");

}}


Enter years of education ===>> 17Enter years of experience ===>> 8You are hired






Enter years of education ===>> 13Enter years of experience ===>> 2You are not qualified

// Java1115.java// This program demonstrates compound decisions with the logical and ( && ) operator.

import java.io.*;



BufferedReader input = new BufferedReader(new InputStreamReader(System.in));int education; // years of educationint experience; // years of work experience

System.out.print("Enter years of education ===>> ");education = Integer.parseInt(input.readLine());System.out.print("Enter years of experience ===>> ");experience = Integer.parseInt(input.readLine());

if ((education >= 16) && (experience >= 5))System.out.println("You are hired");

elseSystem.out.println("You are not qualified");

}}









Java uses || to indicate a logical or.

Java uses && to indicate a logical and.

Java uses ! to indicate a logical not.

Java Logical Operators

// Java1116.java// This program demonstrates compound decision with a do...while loop.// The program checks for proper data entry. The <equals> String method// is used to compare the string values.

import java.io.*;



BufferedReader input = new BufferedReader(new InputStreamReader(System.in));String gender;

do{

System.out.print("Enter your Gender [M/F] ===>> ");gender = input.readLine();

}while (!( gender.equals("M") || gender.equals("F") ));

System.out.println("Your gender is " + gender);

}}


Enter your Gender [M/F] ===>> QEnter your Gender [M/F] ===>> tEnter your Gender [M/F] ===>> 1Enter your Gender [M/F] ===>> fEnter your Gender [M/F] ===>> mEnter your Gender [M/F] ===>> FYour gender is F

// Java1117.java// This program demonstrates compound decision with a do...while loop.// The program does not work properly because of misplaced parentheses.

import java.io.*;




do{


}while (!(gender.equals("M")) || gender.equals("F") );

System.out.println("Your gender is " + gender);

}}


Enter your Gender [M/F] ===>> DEnter your Gender [M/F] ===>> QEnter your Gender [M/F] ===>> FEnter your Gender [M/F] ===>> M

Your gender is M

Correct

while ( !( Gender.equals("M") || Gender.equals("F") ) );

Incorrect

while ( !(Gender.equals("M") ) || Gender.equals("F") );

Watch Your Parentheses

// Java1118.java// This program demonstrates incorrect use of negative compound// decision structure. There will never be correct input.

import java.io.*;




do{


}while (!(gender.equals("M")) || !(gender.equals("F")) );

System.out.println("Your gender is " + gender);}

}


Enter your gender [M/F] ===>> DEnter your gender [M/F] ===>> QEnter your gender [M/F] ===>> FEnter your gender [M/F] ===>> MEnter your gender [M/F] ===>> fEnter your gender [M/F] ===>> m........

Loop never exits. No value satisfies the compound condition.

not(A or B) is equivalent to not(A) and not(B)

not(A and B) is equivalent to not(A) or not(B)

De Morgan’s Law

// Java1119.java// This program demonstrates correct use of negative compound// decision structure using DeMorgan's Law.

import java.io.*;




do{


}

while (!(gender.equals("M")) && !(gender.equals("F")) );System.out.println("Your gender is " + gender);

}}


Enter your Gender [M/F] ===>> QEnter your Gender [M/F] ===>> WEnter your Gender [M/F] ===>> M

Your Gender is M


Enter your Gender [M/F] ===>> F

Your Gender is F

// Java1120.java// This program demonstrates using a boolean data type// with an input protection loop to add readability to a program.

import java.io.*;



BufferedReader input = new BufferedReader(new InputStreamReader(System.in));String gender;boolean correct;do{

System.out.print("Enter your Gender [M/F] ===>> ");gender = input.readLine();correct = (gender.equals("M")) || (gender.equals("F"));if (!correct)

System.out.println("Incorrect input; please re-enter");}while (!correct);System.out.println();System.out.println("Your gender is " + gender);

}}


Enter your Gender [M/F] ===>> qIncorrect input; please re-enterEnter your Gender [M/F] ===>> QIncorrect input; please re-enterEnter your Gender [M/F] ===>> 1Incorrect input; please re-enterEnter your Gender [M/F] ===>> mIncorrect input; please re-enterEnter your Gender [M/F] ===>> M

Your gender is M



Your Gender is F

// Java1121.java// This program accepts upper-case as well as lower-case.// Gender input for [M/F] by using multiple conditional statements.import java.io.*;public class Java1121{


BufferedReader input = new BufferedReader(new InputStreamReader(System.in));String gender;boolean correct;do{

System.out.print("Enter your Gender [M/F] ===>> ");gender = input.readLine();correct = (gender.equals("M")) || (gender.equals("F")) ||

(gender.equals("m")) || (gender.equals("f"));if (!correct)

System.out.println("Incorrect input; please re-enter");}while (!correct);System.out.println();System.out.println("Your gender is " + gender);

}}


Enter your Gender [M/F] ===>> qIncorrect input; please re-enterEnter your Gender [M/F] ===>> QIncorrect input; please re-enterEnter your Gender [M/F] ===>> 1Incorrect input; please re-enterEnter your Gender [M/F] ===>> M

Your gender is M



Your gender is F


Enter your Gender [M/F] ===>> m

Your gender is m


Enter your Gender [M/F] ===>> f

Your gender is f

// Java1122.java// This program shows the need for a practical compound condition// used with an input protection loop.// The program requests the user PIN, but rejects access after three tries.import java.io.*;public class Java1122{


BufferedReader input = new BufferedReader(new InputStreamReader(System.in));String pin;int tries = 0;do{

System.out.print("Enter your PIN ===>> ");pin = input.readLine();tries++;

}while (!pin.equals("8423") && (tries <= 3));if (tries > 4)

System.out.println("You have exceeded your PIN entries");else

System.out.println("Your PIN is accepted");}

}


Please enter your PIN ===>> 4325Please enter your PIN ===>> 4326Please enter your PIN ===>> 4327Please enter your PIN ===>> 4328You have exceeded your PIN entries


Please enter your PIN ===>> 4325Please enter your PIN ===>> 4326Please enter your PIN ===>> 8423Your PIN is accepted

You will see <do..while> used frequently for input protectionloops.

The post-condition loop makes sense for checking erroneous input because you want the program to enter the loop body at least one time.

do…while and Input Protection

A and ( (A or B) and (B or C) and (A or C) or ((B and C) or (A and B)))

This statement is false whenever the first A is false.

In such a situation it is not necessary to check the remainder of the statement.

Short-Circuiting with and

A or ( (A or B) and (B or C) and (A or C) or ((B and C) or (A and B)))

This statement is true whenever the first A is true.

In such a situation it is not necessary to check the remainder of the statement.

Short-Circuiting with or

// Java1123.java// This program uses "short circuiting" but it is not noticeable at all.

import java.io.*;



BufferedReader input = new BufferedReader(new InputStreamReader(System.in));System.out.print("Enter number 1 ===>> ");int n1 = Integer.parseInt(input.readLine());System.out.print("Enter number 2 ===>> ");int n2 = Integer.parseInt(input.readLine());

if (n1 % 2 == 0 && n2 % 2 == 0)System.out.println("Both numbers are even");

elseSystem.out.println("Both numbers are not even");

}}


Enter number 1 ===>> 12Enter number 2 ===>> 24Both numbers are even


Enter number 1 ===>> 12Enter number 2 ===>> 15Both numbers are not even


Enter number 1 ===>> 15Enter number 2 ===>> 31Both numbers are not even

You have seen return methods that return integers and real numbers. Method isEven returns true or false, since it is a boolean return method. The purpose of the method is to return true if the method argument number is even and false if number is odd. It also generates output so we can see that the method was called. The purpose of this method is to help explain short circuiting in the next couple program examples.

The isEven Method

public static boolean isEven(int Number) { System.out.println(); System.out.println("Calling isEven Method"); System.out.println(); if (Number % 2 == 0) return true; else return false; }

// Java1124.java// This program uses "short circuiting" and uses the isEven// method to demonstrate short circuiting with logical or.

import java.io.*;



BufferedReader input = new BufferedReader(new InputStreamReader(System.in));System.out.print("Enter number 1 ===>> ");int n1 = Integer.parseInt(input.readLine());System.out.print("Enter number 2 ===>> ");int n2 = Integer.parseInt(input.readLine());if (isEven(n1) || isEven(n2))

System.out.println("One or more numbers are even");else

System.out.println("Neither numbers are even");}

public static boolean isEven(int number){

System.out.println();System.out.println("Calling isEven Method");System.out.println();if (number % 2 == 0)

return true;else

return false;}

}


Enter number 1 ===>> 12Enter number 2 ===>> 24

Calling IsEven Method

One or more numbers are even



Calling IsEven Method

One or more numbers are even



Calling isEven Method


Neither numbers are even

// Java1125.java// This program uses "short circuiting" and uses the isEven// method to demonstrate short circuiting with logical and.

import java.io.*;



BufferedReader input = new BufferedReader(new InputStreamReader(System.in));System.out.print("Enter number 1 ===>> ");int n1 = Integer.parseInt(input.readLine());System.out.print("Enter number 2 ===>> ");int n2 = Integer.parseInt(input.readLine());if (isEven(n1) && isEven(n2))

System.out.println("Both numbers are even");else

System.out.println("Both numbers are not even");}

public static boolean isEven(int number){

System.out.println();System.out.println("Calling IsEven Method");System.out.println();if (number % 2 == 0)

return true;else

return false;}

}





Both numbers are even





Both numbers are not even




Both numbers are not even

Recursion is the process of a method calling itself.

Recursion Definition

// Java1126.java// This program introduces recursion as an alternative to repetition.// This example creates an infinite loop.



count();}

private static int x = 1000;

public static void count(){

x++;System.out.println("x = " + x);count();

}

}


X = 1001X = 1002X = 1003X = 1004X = 1005X = 1006X = 1007X = 1008X = 1009X = 1010........

DOES NOT END

It is easy to write programs with recursive methods thatrepeat in an infinite pattern of recursive calls. Some special condition must be tested before each recursive call is made.

Recursion Warning

// Java1127.java// This program introduces recursion as an alternative to repetition. The // Count method includes a conditional statement to end the recursive calls.



count();}

private static int x = 1000;

public static void count(){

x++;System.out.println("x = " + x);if (x < 1200)

count();}

}


X = 1001X = 1002X = 1003X = 1004X = 1005X = 1006X = 1007X = 1008X = 1009.........

X = 1197X = 1198X = 1199X = 1200

Recursion is the process of a method calling itself.

Recursion simulates repetition.

Recursion requires some condition that exits the recursive calling to prevent infinite repetition. The variable value that makes the condition true and stops the recursive calls is called the base case or exit

You will find in some future topics that there exist a variety of programming problems that are easier to solve with recursive structures than with iterative loop structures.

Recursion Notes

The exercises that follow will be in the same pattern as the exercises presented in previous chapters. Each exercise presents a brief program with the mission to determine the program output. The essence of the exercise revolves around tracing the variable values as they change during program execution. This time the exercises will be more challenging with the addition of nested control structures and compound conditions.

The question in all of these is “What is the output of this program?”

Worked-Out Exercises

// EX1101.java

public class Ex1101{ public static void main(String args[]) { for (int x = 1; x < 2; x++) for (int y = 1; y < 3; y++) System.out.println(x + " " + y); }} Ex1101.java Answer

x y Output

1 1 1 11 2 1 2

// Ex1102.java

public class Ex1102{


for (int x = 1; x < 3; x++){

for (int y = 1; y < 4; y++)System.out.print(x*y + " ");

System.out.println();}

}}

Ex1102.java Answer

x y Output

1 1 11 2 1 21 3 1 2 32 1 22 2 2 42 3 2 4 6

// Ex1103.java



int x = 5;int k,y;while (x <= 8){

y = 1;while (y <= 7){

y++;k = x + y;System.out.println(y + " " + k);

}x += y;System.out.println("x = " + x);

} }

}

Ex1103.java Answer

y k x Output5

12 73 84 95 106 117 128 13 13

k = 13

An OBOB is an Off By One Bug error.

This problem occurs at the boundaries of control structures.

Carefully check your program code at the boundaries to avoid OBOBs.

OBOB Warning!

// Ex1104.java



int a = 1, b = 2, c = 3, d = 4;while (a < b && c < d){

a = c + d;c = a + b;

}System.out.println(a + b + c + d);

}}

Ex1104.java Answer

a b c d Output1 2 3 47 9

7294

// Ex1105.java



int a;int b = 2;for (int k = 0; k < 4; k++){

a = k;b += k;while (a < b){

System.out.println(a + " " + b);a += b;b += k;

}}

}}

Ex1105.java Answer

k a b Output2

0 0 2 0 22 2

1 1 3 1 3 4 42 2 6 2 6

8 83 3 11 3 11

14 14

// Ex1106.java



int a = 0;int b = 10;for (int k = a; k < b; k++){

a++;b--;System.out.println(a + " " + b + " " + k);

}}

}

Ex1106.java Answer

k a b Output

0 100 1 9 1 9 01 2 8 2 8 12 3 7 3 7 23 4 6 4 7 34 5 5 5 5 4 5

// Ex1107.java



int t = 0;for (int p = 1; p <= 4; p++)

for (int q = 1; q <= 4; q++)t++;

System.out.println("t = " + t);}

}

Ex1107.java Answer

p q t Output0

1 1 12 23 34 4

2 1 52 63 74 8

3 1 92 103 114 12

4 1 132 143 154 16

t = 16

// Ex1108.java



int t = 0;for (int p = 0; p < 10; p++)

for (int q = 1; q < 10-p; q++)t++;

System.out.println("t = " + t);}

}

Ex1108.java Answer

p q t Output0

0 1 12 23 34 45 56 67 78 89 9

1 1 102 113 124 135 146 157 168 17

2 1 182 193 204 215 226 237 24

3 1 252 263 274 285 296 30

4 1 312 323 334 345 35

5 1 362 373 384 39

6 1 402 413 42

7 1 432 44

8 1 45

t = 45

// Ex1109.CPP



int n1, n2, n3;n1 = n2 = n3 = 1;for (int k = 3; k <= 10; k++){

n3 = n1 + n2;n1 = n2;n2 = n3;

}System.out.println("n3 = " + n3);

}}

Ex1109.java Answer

k n3 n1 n2 Output1 1 1

3 2 1 24 3 2 35 5 3 56 8 5 87 13 8 138 21 13 219 34 21 3410 55 34 55

n3 = 55

// Ex1110.java



int a = 5;int b = 10;int c = 13;while (a < b && b != c){

a += 2;b++;if ((a + b) % 2 == 0)

c++;}System.out.println(a + " " + b + " " + c);

}}

Ex1110.java Answer

a b c a < b b != c Output5 10 13 true true7 11 14 true true9 12 true true11 13 15 true true13 14 true true15 15 16 false true

15 15 16

// Ex1111 THE MYSTERY PROGRAMimport java.io.*;public class Ex1111{


BufferedReader input = new BufferedReader(new InputStreamReader(System.in));int a, b , c;System.out.print("Enter integer 1 ===>> ");a = Integer.parseInt(input.readLine());System.out.print("Enter integer 2 ===>> ");b = Integer.parseInt(input.readLine());if (a < b)

if (b < a)c = 1000;

elsec = 2500;

elseif (b > a)

c = 2000;else

c = 2500;System.out.println("c = " + c);

}}

Ex1111.java Answer

a b c Output? ? ? C = 2500

// Ex1112.java



for (int x = 1; x <= 4; x++){

for (int y = 1; y <= 4; y++)System.out.print(x + y + " ");

System.out.println();}

}}

Ex1112.java Answer

x y x + y1 1 21 2 31 3 41 4 52 1 32 2 42 3 52 4 63 1 43 2 53 3 63 4 74 1 54 2 64 3 74 4 8

2 3 4 53 4 5 64 5 6 75 6 7 8

FINALOUTPUT

chapter 11 slides

Documents

keyboard text input

readline line

bufferedreader input

user input

object input

numeric input

user keyboard input

readlinethe input