Liang,Introduction to Java Programming,revised by Dai-kaiyu1 Chapter 3 Control Statements 选择是艰难的谁能控制自己的命运？

Liang,Introduction to Java Programming,revised by Dai-kaiyu 1

Chapter 3 Control Statements

Chapter 1 Introduction to Computers, Programs, and Java

Chapter 2 Primitive Data Types and Operations

Chapter 3 Control Statements

Chapter 5 Arrays

Chapter 4 Methods

Basic computer skills such as using Windows, Internet Explorer, and Microsoft Word

Prerequisites for Part I

选择是艰难的

谁能控制自己的命运？


Objectives• To understand the flow of control in selection and loop statements

(§3.2-3.7).• To use Boolean expressions to control selection statements and loop

statements (§3.2-3.7).• To implement selection control using if and nested if statements

(§3.2).• To implement selection control using switch statements (§3.2).• To write expressions using the conditional operator (§3.2).• To use while, do-while, and for loop statements to control the

repetition of statements (§3.4).• To write nested loops (§3.4).• To know the similarities and differences of three types of loops

(§3.5).• To implement program control with break and continue (§3.6).

Liang,Introduction to Java Programming,revised by Dai-kaiyu3

Algorithms

Algorithm Series of actions in specific order

The actions executed The order in which actions execute

Program control Specifying the order in which actions execute

Control structures help specify this order


PseudocodePseudocode

Informal language for developing algorithms Not executed on computers Helps developers “think out” algorithms Normally describes only executable

statementsif student’s grade is greater then or equal to 60

Print " Passed"

if(grade>=60)

System.out.println(“Passed");


Control Structures

Sequential execution Program statements execute one after the other

Transfer of control Three control statements can specify order of

statements Sequence structure (built in Java) Selection structure Repetition structure

Flowchart Graphical representation of algorithm

Flowlines indicate order in which actions execute


add grade to total total = total + grade;

add 1 to counter counter = counter + 1 ;

Flowcharting Java’s sequence structure.

Flowlines

Action Symbols

Connector Symbols


grade >= 60true

false

print “Passed”

Flowcharting the single-selection if structure.

Decision Symbol


Selection Statements

if Statements

switch Statements

Conditional Operators


Simple if Statements

Boolean Expression

true

Statement(s)

false (radius >= 0)

true

area = radius * radius * PI; System.out.println("The area for the circle of " + "radius " + radius + " is " + area);

false

(A) (B)

if (booleanExpression) { statement(s);}

if (radius >= 0) { area = radius * radius * PI; System.out.println("The area" + “ for the circle of radius " + radius + " is " + area);}


Note

if ((i > 0) && (i < 10)) { System.out.println("i is an " + + "integer between 0 and 10"); }

(a)

Equivalent

(b)

if ((i > 0) && (i < 10)) System.out.println("i is an " + + "integer between 0 and 10");

Outer parentheses required Braces can be omitted if the block contains a single statement


Caution

Adding a semicolon at the end of an if clause is a common mistake.

if (radius >= 0);

{

area = radius*radius*PI;

System.out.println(

"The area for the circle of radius " +

radius + " is " + area);

}logic error. This error often occurs when you use the next-line block style.

Wrong


The if...else Statementif (booleanExpression) { statement(s)-for-the-true-case;}else { statement(s)-for-the-false-case;}

Boolean Expression

false true

Statement(s) for the false case Statement(s) for the true case

What if there is no else statement, the difference

Can’t use 0,1


if...else Example

if (radius >= 0) { area = radius * radius * 3.14159;

System.out.println("The area for the “ + “circle of radius " + radius + " is " + area);}else { System.out.println("Negative input");}


Multiple Alternative if Statements

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';

Equivalent

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';

better


Trace if-else statement

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';

Suppose score is 70.0 The condition is false




Suppose score is 70.0 The condition is false




Suppose score is 70.0 The condition is true




Suppose score is 70.0 grade is C




Suppose score is 70.0 Exit the if statement


NoteThe else clause matches the most recent if clause in the same block.

int i = 1; int j = 2; int k = 3; if (i > j) if (i > k) System.out.println("A"); else System.out.println("B");

(a)

Equivalent

(b)

int i = 1; int j = 2; int k = 3; if (i > j) if (i > k) System.out.println("A"); else System.out.println("B");


Note, cont.To force the else clause to match the first if clause: int i = 1;

int j = 2;

int k = 3;

if (i > j) {

if (i > k)

System.out.println("A");

}

else

System.out.println("B");

This statement prints B.


TIP

if (number % 2 == 0) even = true; else even = false;

(a)

Equivalent boolean even = number % 2 == 0;

(b)


CAUTION

if (even == true) System.out.println( "It is even.");

(a)

Equivalent if (even) System.out.println( "It is even.");

(b)

better

if (even = true)

statement;

compare


1 // Fig. 2.20: Comparison.java2 // Compare integers using if structures, relational operators 3 // and equality operators.4 5 // Java extension packages6 import javax.swing.JOptionPane;7 8 public class Comparison {9 10 // main method begins execution of Java application11 public static void main( String args[] )12 {13 String firstNumber; // first string entered by user14 String secondNumber; // second string entered by user15 String result; // a string containing the output16 int number1; // first number to compare17 int number2; // second number to compare18 19 // read first number from user as a string20 firstNumber =21 JOptionPane.showInputDialog( "Enter first integer:" );22 23 // read second number from user as a string24 secondNumber =25 JOptionPane.showInputDialog( "Enter second integer:" );26 27 // convert numbers from type String to type int28 number1 = Integer.parseInt( firstNumber );29 number2 = Integer.parseInt( secondNumber );30 31 // initialize result to empty String32 result = "";33 Can we omit this statement?


34 if ( number1 == number2 )35 result = number1 + " == " + number2;36 37 if ( number1 != number2 )38 result = number1 + " != " + number2;39 40 if ( number1 < number2 )41 result = result + "\n" + number1 + " < " + number2;42 43 if ( number1 > number2 )44 result = result + "\n" + number1 + " > " + number2;45 46 if ( number1 <= number2 )47 result = result + "\n" + number1 + " <= " + number2;48 49 if ( number1 >= number2 )50 result = result + "\n" + number1 + " >= " + number2;51 52 // Display results53 JOptionPane.showMessageDialog(54 null, result, "Comparison Results",55 JOptionPane.INFORMATION_MESSAGE );56 57 System.exit( 0 ); // terminate application58 59 } // end method main60 61 } // end class Comparison

Test for equality, create new string, assign to result.

Notice use of JOptionPane.INFORMATION_MESSAGE


lengthy statement split after comma, operator,…,indent

JOptionPane.showMessageDialog( null, result, “Comparison Results　Ｗ　　ＡＳ　” + “ASASA DA DSA DAS DAS “, JOptionPane.INFORMATION_MESSAGE );

In main method, we always do not put such trivial statements.


Program Output


Example 3.1 Computing Taxes

The US federal personal income tax is calculated based on the filing status and taxable income. There are four filing statuses: single filers, married filing jointly, married filing separately, and head of household. The tax rates for 2002 are shown in Table 3.1.


Example 3.1 Computing Taxes, cont.

Compute TaxWithSelectionStatementCompute TaxWithSelectionStatement Run

if (status == 0) { // Compute tax for single filers}else if (status == 1) { // Compute tax for married file jointly}else if (status == 2) { // Compute tax for married file separately}else if (status == 3) { // Compute tax for head of household}else { // Display wrong status}

Computer may think none of the branch will excute. Thus cause errors

Common Error Not initializing before using a variable in method


switch Statementsswitch (status) { case 0: compute taxes for single filers; break; case 1: compute taxes for married file jointly; break; case 2: compute taxes for married file separately; break; case 3: compute taxes for head of household; break; default: System.out.println("Errors: invalid status"); System.exit(0);}


switch Statement Flow Chart

status is 0 Compute tax for single filers break

Compute tax for married file jointly break status is 1

Compute tax for married file separatly break status is 2

Compute tax for head of household break status is 3

Default actions default

Next Statement


switch Statement Rules

switch (switch-expression) { case value1: statement(s)1; break; case value2: statement(s)2; break; … case valueN: statement(s)N; break; default: statement(s)-for-default;}

The switch-expression must yield a value of char, byte, short, or int type and must always be enclosed in parentheses.

The value1, ..., and valueN must have the same data type as the value of the switch-expression. The resulting statements in the case statement are executed when the value in the case statement matches the value of the switch-expression. Note that value1, ..., and valueN are constant expressions, meaning that they cannot contain variables in the expression, such as 1 + x.


switch Statement Rules

The keyword break is optional, but it should be used at the end of each case in order to terminate the remainder of the switch statement. If the break statement is not present, the next case statement will be executed.

switch (switch-expression) { case value1: statement(s)1; break; case value2: statement(s)2; break; … case valueN: statement(s)N; break; default: statement(s)-for-default;}The default case, which is

optional, can be used to perform actions when none of the specified cases matches the switch-expression. The case statements are executed in sequential order, but

the order of the cases (including the default case) does not matter. However, it is good programming style to follow the logical sequence of the cases and place the default case at the end.


Switch 语句的落空

在 switch语句中，你通常在每一种 case情况后都应使用 break语句，否则，第一个相等情况后面所有的语句都会被执行，这种情况叫做落空

TestSwitch.java

下面程序的输出结果是什么

TestSwitch1.java

TestSwitch2.java

TestSwitch3.java


Conditional operator (?:) Java’s only ternary operator-takes three operands(Ternary ;Binary ;Unary )

Grammer

Variable = booleanexpression ? expression1 : expression2

If (booleanexpression)

variable = expression1;

else

variable = expression2;


Conditional Operator

if (x > 0) y = 1else y = -1;

is equivalent to

y = (x > 0) ? 1 : -1;(booleanExpression) ? expression1 :

expression2


Conditional Operator

if (num % 2 == 0)

System.out.println(num + “is even”);else System.out.println(num + “is odd”);

System.out.println( (num % 2 == 0)? num + “is even” : num + “is odd”);


Repetitions

while Loops

do-while Loopsfor Loops

break and continue


while Loop Flow Chart

while (loop-continuation-condition) {

// loop-body;

Statement(s);

}

int count = 0;

while (count < 100) {

System.out.println("Welcome to Java!");

count++;

}

Loop Continuation Condition?

true

Statement(s) (loop body)

false (count < 100)?

true

System.out.println("Welcome to Java!"); count++;

false

(A) (B)

count = 0;


Trace while Loop

int count = 0;

while (count < 2) {


count++;

}

Initialize count


Trace while Loop, cont.

int count = 0;

while (count < 2) {


count++;

}

(count < 2) is true



int count = 0;

while (count < 2) {


count++;

}

Print Welcome to Java



int count = 0;

while (count < 2) {


count++;

}

Increase count by 1count is 1 now



int count = 0;

while (count < 2) {


count++;

}

(count < 2) is still true since count is 1



int count = 0;

while (count < 2) {


count++;

}




int count = 0;

while (count < 2) {


count++;

}

Increase count by 1count is 2 now



int count = 0;

while (count < 2) {


count++;

}

(count < 2) is false since count is 2 now


Trace while Loop

int count = 0;

while (count < 2) {


count++;

}

The loop exits. Execute the next statement after the loop.

Avoid infinite loops


Example 3.2: Using while Loops

Problem: Write a program that reads and calculates the sum of an unspecified number of integers. The input 0 signifies the end of the input.

TestWhileTestWhile Run


Caution

Don’t use floating-point values for equality checking in a loop control.

// data should be zerodouble data = Math.pow(Math.sqrt(2), 2) - 2; if (data == 0) System.out.println("data is zero");else System.out.println("data is not zero");

Demo FloatNotPrecise.java


Formulating Algorithms with Top-Down, Stepwise Refinement (Sentinel-Controlled Repetition)

Sentinel value Used to indicated the end of data entry Also called a signal value, flag value

Average2.java has indefinite repetition Indefinite repetition: the number of repetitions is not

known before the loop begins executing. User enters sentinel value (-1) to end repetition


Initialize total to zeroInitialize counter to zero

Input the first grade (possibly the sentinel)

While the user has not as yet entered the sentinel Add this grade into the running totalAdd one to the grade counterInput the next grade (possibly the sentinel)

If the counter is not equal to zeroSet the average to the total divided by the counterPrint the average

elsePrint “No grades were entered”

Pseudocode algorithm that uses sentinel-controlled repetition to solve the class-average problem.

Determine the class average for the quiz

Initialize variables

Input,sum up and count the quiz grades

Calculate and print the class average


Average2.java

1 // Fig. 4.9: Average2.java2 // Class average program with sentinel-controlled repetition.3 4 // Java core packages5 import java.text.DecimalFormat;6 7 // Java extension packages8 import javax.swing.JOptionPane;9 10 public class Average2 {11 12 // main method begins execution of Java application13 public static void main( String args[] )14 {15 int gradeCounter, // number of grades entered16 gradeValue, // grade value17 total; // sum of grades18 double average; // average of all grades19 String input; // grade typed by user20 21 // Initialization phase22 total = 0; // clear total23 gradeCounter = 0; // prepare to loop24 25 // Processing phase26 // prompt for input and read grade from user27 input = JOptionPane.showInputDialog(28 "Enter Integer Grade, -1 to Quit:" );29 30 // convert grade from a String to an integer31 gradeValue = Integer.parseInt( input );32


33 while ( gradeValue != -1 ) {34 35 // add gradeValue to total36 total = total + gradeValue;37 38 // add 1 to gradeCounter39 gradeCounter = gradeCounter + 1;40 41 // prompt for input and read grade from user42 input = JOptionPane.showInputDialog(43 "Enter Integer Grade, -1 to Quit:" );44 45 // convert grade from a String to an integer46 gradeValue = Integer.parseInt( input );47 }48 49 // Termination phase50 DecimalFormat twoDigits = new DecimalFormat( "0.00" );51 52 if ( gradeCounter != 0 ) {53 average = (double) total / gradeCounter; 54 55 // display average of exam grades56 JOptionPane.showMessageDialog( null,57 "Class average is " + twoDigits.format( average ),58 "Class Average", JOptionPane.INFORMATION_MESSAGE );59 }60 else61 JOptionPane.showMessageDialog( null,62 "No grades were entered", "Class Average",63 JOptionPane.INFORMATION_MESSAGE );64 65 System.exit( 0 ); // terminate application66

loop until gradeValue equals sentinel value (-1)

Format numbers to nearest hundredth

Return a String


Average2.java67 } // end method main68 69 } // end class Average2


double x=70.89771;DecimalFormat y = new DecimalFormat("0.000");System.out.println(y.format( x ));

New operator Creates an object as the program executes by obtaining

enough memory to store an object of the type specified to the right of new

Dynamic memory allocation operator Object of Class String is instantiated automatically

DecimalFormat objects format number


average = (double) total / gradeCounter;

Explicit conversionThe value stored in total is still an integerTemporary double version of total created

Promotion(implicit conversion)Cast operators

Parentheses around the name of a data typeFloat-points number are not always 100% precise


do-while Loop

do {

// Loop body;

Statement(s);

} while (loop-continuation-condition);


true


false


Components of a typical for structure header.

for Loops


for Loopsfor (initial-action; loop-

continuation-condition; action-after-each-iteration) {

// loop body; Statement(s);}

int i;for (i = 0; i < 100; i++) { System.out.println( "Welcome to Java!"); }


true


false

(A)

Action-After-Each-Iteration

Intial-Action

(i < 100)?

true

System.out.println( "Welcome to Java");

false

(B)

i++

i = 0

Can be any statement


Trace for Loop


Initialize count


Trace for Loop, cont.


Execute initializeri is now 0




(i < 2) is true since i is 0



int i;for (i = 0; i < 2; i++) { System.out.println("Welcome to Java!"); }





Execute adjustment statement i now is 1




(i < 2) is still true since i is 1








Execute adjustment statement i now is 2




(i < 2) is false since i is 2



int i;for (i= 0; i < 2; i++) { System.out.println("Welcome to Java!"); }

Exit the loop. Execute the next statement after the loop

Control variable’s scope: i can’t be used after the body of the structure,if variable i is defined inside the for structure

Three parts of the for structure can be omitted, but the semicolon can’t

What if here is 2


NoteThe initial-action in a for loop can be a list of zero or more comma-separated expressions.

The action-after-each-iteration in a for loop can be a list of zero or more comma-separated statements.

for (int i = 1; i < 100; System.out.println(i++));

for (int i = 0, j = 0; (i + j < 10); i++, j++) { // Do something}


NoteIf the loop-continuation-condition in a for loop is omitted, it is implicitly true.

for ( ; ; ) { // Do something } (a)

Equivalent while (true) { // Do something }

(b)

(b) Is recommended to avoid confusion


Example 3.3 Using for Loops

Problem: Write a program that sums a series that starts with 0.01 and ends with 1.0. The numbers in the series will increment by 0.01, as follows: 0.01 + 0.02 + 0.03 and so on.

TestSumTestSum Run


Example 3.4 Displaying the Multiplication Table

Problem: Write a program that uses nested for loops to print a multiplication table.

TestMultiplicationTableTestMultiplicationTable

Run


Which Loop to Use?The three forms of loop statements, while, do-while, and for, are expressively equivalent; that is, you can write a loop in any of these three forms.

for (initial-action; loop-continuation-condition; action-after-each-iteration) { // Loop body; }

(A)

Equivalent

(B)

initial-action; while (loop-continuation-condition) { // Loop body; action-after-each-iteration; }

while (loop-continuation-condition) { // Loop body }

(A)

Equivalent

(B)

for ( ; loop-continuation-condition; ) { // Loop body }


Recommendationsuse the one that is most intuitive and comfortable for you.

In general, a for loop may be used if the number of repetitions is known, as, for example, when you need to print a message 100 times.

A while loop may be used if the number of repetitions is not known, as in the case of reading the numbers until the input is 0.

A do-while loop can be used to replace a while loop if the loop body has to be executed before testing the continuation condition.


Caution

Adding a semicolon at the end of the for clause before the loop body is a common mistake, as shown below:

for (int i=0; i<10; i++);

{

System.out.println("i is " + i);

}

Logic Error


Caution, cont.Similarly, the following loop is also wrong:int i=0; while (i < 10);{ System.out.println("i is " + i); i++;}

In the case of the do loop, the following semicolon is needed to end the loop.int i=0; do { System.out.println("i is " + i); i++;} while (i<10);

Logic Error

Correct


Statements break and continue

break/continue Alter flow of control

break statement Causes immediate exit from control structure

Used in while, for, do/while or switch statements

continue statement Skips remaining statements in loop body Proceeds to next iteration

Used in while, for or do/while statements


Using the Keywords break and continue


The continue Keyword


Using break and continue

Examples for using the break and continue keywords:

Example 3.5: TestBreak.java

Example 3.6: TestContinue.java

TestBreakTestBreak

TestContinueTestContinue

Run

Run


Labeled break and continue Statements

Every statement in Java can have an optional label

Labeled block Set of statements enclosed by {} Preceded by a label

Labeled break statement Exit from nested control structures Proceeds to end of specified labeled block

Labeled continue statement Skips remaining statements in nested-loop body Proceeds to beginning of specified labeled block


1 // Fig. 5.13: BreakLabelTest.java2 // Using the break statement with a label3 4 // Java extension packages5 import javax.swing.JOptionPane;6 7 public class BreakLabelTest {8 9 // main method begins execution of Java application10 public static void main( String args[] )11 {12 String output = "";13 14 stop: { // labeled block15 16 // count 10 rows17 for ( int row = 1; row <= 10; row++ ) {18 19 // count 5 columns20 for ( int column = 1; column <= 5 ; column++ ) {21 22 // if row is 5, jump to end of "stop" block23 if ( row == 5 )24 break stop; // jump to end of stop block25 26 output += "* ";27 28 } // end inner for structure29 30 output += "\n";31 32 } // end outer for structure33 34 // the following line is skipped35 output += "\nLoops terminated normally";

Loop 10 times

stop is the labeled block

Exit to line 37 (next slide)

Nested loop 5 times


36 37 } // end labeled block38 39 JOptionPane.showMessageDialog(40 null, output,"Testing break with a label",41 JOptionPane.INFORMATION_MESSAGE );42 43 System.exit( 0 ); // terminate application44 45 } // end method main46 47 } // end class BreakLabelTest


1 // Fig. 5.14: ContinueLabelTest.java2 // Using the continue statement with a label3 4 // Java extension packages5 import javax.swing.JOptionPane;6 7 public class ContinueLabelTest {8 9 // main method begins execution of Java application10 public static void main( String args[] )11 {12 String output = "";13 14 nextRow: // target label of continue statement15 16 // count 5 rows17 for ( int row = 1; row <= 5; row++ ) {18 output += "\n";19 20 // count 10 columns per row21 for ( int column = 1; column <= 10; column++ ) {22 23 // if column greater than row, start next row24 if ( column > row )25 continue nextRow; // next iteration of26 // labeled loop27 28 output += "* ";29 30 } // end inner for structure31 32 } // end outer for structure33

nextRow is the labeled block

Loop 5 times

Nested loop 10 times

continue to line 14 (nextRow)


34 JOptionPane.showMessageDialog(35 null, output,"Testing continue with a label",36 JOptionPane.INFORMATION_MESSAGE );37 38 System.exit( 0 ); // terminate application39 40 } // end method main41 42 } // end class ContinueLabelTest


Example 3.7 Finding the Greatest Common Divisor

Problem: Write a program that prompts the user to enter two positive integers and finds their greatest common divisor.

GreatestCommonDivisorGreatestCommonDivisor RunRun


Example 3.8 Finding the Sales Amount

Problem: You have just started a sales job in a department store. Your pay consists of a base salary and a commission. The base salary is $5,000. The scheme shown below is used to determine the commission rate.

Sales Amount Commission Rate$0.01–$5,000 8 percent$5,000.01–$10,000 10 percent$10,000.01 and above 12 percent

Your goal is to earn $30,000 in a year. Write a program that will find out the minimum amount of sales you have to generate in order to make $25,000.

FindSalesAmountFindSalesAmount RunRun


Example 3.9 Displaying a Pyramid of Numbers

Problem: Write a program that prompts the user to enter an integer from 1 to 15 and displays a pyramid. For example, if the input integer is 12, the output is shown below.

PrintPyramidPrintPyramid RunRun

(numberOfLines-row)*3

Three parts


Example 3.10 Displaying Prime Numbers

Problem: Write a program that displays the first 50 prime numbers in five lines, each of which contains 10 numbers. An integer greater than 1 is prime if its only positive divisor is 1 or itself. For example, 2, 3, 5, and 7 are prime numbers, but 4, 6, 8, and 9 are not.

Solution: The problem can be broken into the following tasks:•For number = 2, 3, 4, 5, 6, ..., test whether the number is prime.•Determine whether a given number is prime.•Count the prime numbers.•Print each prime number, and print 10 numbers per line.

PrimeNumberPrimeNumber RunRun


QUIZ

Identify and correct the errors in each of the following. a. if ( age >= 65 ); System.out.println( "Age greater than or equal to 65" ); else System.out.println( "Age is less than 65 )"; b. int x = 1, total;

while ( x <= 10 ) { total += x;

++x; }a. While ( x <= 100 ) total += x;

++x; b. while ( y > 0 ) {

System.out.println( y );++y;


Answer a. if ( age >= 65 ); System.out.println( "Age greater than or equal to 65" ); else System.out.println( "Age is less than 65 )"; b. int x = 1, total;

while ( x <= 10 ) { total += x;

++x; }c. While ( x <= 100 ) total += x;

++x; d. int y = 5; while ( y > 0 ) {

System.out.println( y );++y;

a.Semicolon at the end of the if condition should be removed. The closing double quote of the second System.out.println should be inside of the closing parenthesis.

b. The variable total should be initialized to zero.

d. The ++ operator should be changed to --. The closing curly brace for the while loop is missing.

c. The W in While should be lowercase. The two statements should be enclosed in curly braces to properly group them into the body of the while; otherwise the loop will be an infinite loop


Find the error in each of the following. [Note: There may be more than one error.]a.For ( x = 100, x >= 1, x++ ) System.out.println( x );

b.The following code should print whether integer value is odd or even:switch ( value % 2 ) { case 0: System.out.println( "Even integer" ); case 1: System.out.println( "Odd integer" );}

c.The following code should output the odd integers from 19 to 1:for ( x = 19; x >= 1; x += 2 ) System.out.println( x );

d.The following code should output the even integers from 2 to 100:counter = 2;do { System.out.println( counter ); counter += 2;} While ( counter < 100 );


Find the error in each of the following. [Note: There may be more than one error.]a.For ( x = 100, x >= 1, x++ ) System.out.println( x );

b.The following code should print whether integer value is odd or even:switch ( value % 2 ) { case 0: System.out.println( "Even integer" ); case 1: System.out.println( "Odd integer" );}

c.The following code should output the odd integers from 19 to 1:for ( x = 19; x >= 1; x += 2 ) System.out.println( x );

d.The following code should output the even integers from 2 to 100:counter = 2;do { System.out.println( counter ); counter += 2;} While ( counter < 100 );

The F in for should be lowercase. Semicolons should be used in the for header instead of commas. ++ should be --

A break statement should be placed in case 0

+= should be -=

The W in While should be lowercase. < should be <=

Documents

Liang,Introduction to Java Programming,revised by Dai-kaiyu1 Chapter 3 Control Statements 选择是艰难的 谁能控制自己的命运？

Liang,Introduction to Java Programming,revised by Dai-kaiyu1 Chapter 3 Control Statements 选择是艰难的谁能控制自己的命运？