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9 cm604.11

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  • Chapter 6 -
  • Chapter 6 - Notice that the if–then statement is not necessary, because we can write any if–then statement using if–then–else by including no statement in the else block. For instance, the sample if–then statement can be written as if (testScore >= 95) { messageBox.show("You are an honor student"); } else { } In this book, we use if-then statements whenever appropriate.
  • Chapter 6 -
  • Chapter 6 -
  • Chapter 6 -
  • Chapter 6 -
  • Chapter 6 - It is possible to write if tests in different ways to achieve the same result. For example, the above code can also be expressed as if (testScore >= 70 && studentAge < 10) { messageBox.show("You did a great job"); } else { //either testScore < 70 OR studentAge >= 10 if (testScore >= 70) { messageBox.show("You did pass"); } else { messageBox.show("You did not pass"); } }
  • Chapter 6 -
  • Chapter 6 - Rules for writing the then and else blocks: - Left and right braces are necessary to surround the statements if the then or else block contains multiple statements. - Braces are not necessary if the then or else block contains only one statement. - A semicolon is not necessary after a right brace.
  • Chapter 6 - In this book, we will use Style 1, mainly because this style is more common among programmers. If you prefer Style 2, then go ahead and use it. Whichever style you choose, be consistent, because consistent look and feel are very important to make your code readable.
  • Chapter 6 - If we follow the general rule, the above if-else if will be written as below, but the style shown in the slide is the standard notation. if (score >= 90) messageBox.show("Your grade is A"); else if (score >= 80) messageBox.show("Your grade is B"); else if (score >= 70) messageBox.show("Your grade is C"); else if (score >= 60) messageBox.show("Your grade is D"); else messageBox.show("Your grade is F");
  • Chapter 6 - If we follow the general rule, the above if-else if will be written as below, but the style shown in the slide is the standard notation. if (score >= 90) messageBox.show("Your grade is A"); else if (score >= 80) messageBox.show("Your grade is B"); else if (score >= 70) messageBox.show("Your grade is C"); else if (score >= 60) messageBox.show("Your grade is D"); else messageBox.show("Your grade is F");
  • Chapter 6 - If you want the else to match with the first if , then you have to write if (x < y) { if (x < z) messageBox.show("Hello"); } else messageBox.show("Good bye");
  • Chapter 6 - If you want the else to match with the first if , then you have to write if (x < y) { if (x < z) messageBox.show("Hello"); } else messageBox.show("Good bye");
  • Chapter 6 -
  • Chapter 6 -
  • Chapter 6 -
  • Chapter 6 -
  • Chapter 6 -
  • Transcript

    • 1. selection statements of Java 1
    • 2. ObjectiveOn completion of this period you would be able to know• Various selection statements available in Java 2
    • 3. Recap• In the previous class we have discussed • Various types of operators 3
    • 4. Selection statements of Java• Java language supports the following selection statements• If statement• Switch statement• Conditional operator statement 4
    • 5. The if Statement if ( <boolean expression> ) { <then block> } Boolean Boolean Expression Expression if ( testScore >= 95 ){Then Then System.out.println("You are a good student");BlockBlock } 5
    • 6. Control Flow of if testScore >= true testScore >= 95? 95? System.out.println System.out.println false ("You are aagood student"); ("You are good student"); 6
    • 7. The if-else Statementif (testScore < 50) { This statement is This statement is System. out. println ("You did not pass"); executed ififthe testScore executed the testScore is less than 50. is less than 50.} else { This statement is This statement is System. out. println ("You did pass"); executed ififthe testScore executed the testScore is 50 or higher. is 50 or higher.} 7
    • 8. Syntax for the if-else Statement if ( <boolean expression> ) { <then block> } else { Boolean Boolean <else block> } Expression Expression if (testScore < 50) { System.out.println("You did not pass"); Then Then Block Block } else { System.out.println("You did pass");else Blockelse Block } 8
    • 9. Control Flow false true testScore < 50 ?? testScore < 50 System.out.println System.out.printlnSystem.out.println System.out.println ("You did not ("You did not("You did pass"); ("You did pass"); pass"); pass"); 9
    • 10. The Nested-if Statement• The then and else block of an if statement can contain any valid statements, including other if statements. An if statement containing another if statement is called a nested-if statement if (testScore >= 50) { if (studentAge < 10) { System.out.println("You did a great job"); } else { System.out.println("You did pass"); } } else { //test score < 70 System.out.println("You did not pass"); } 10
    • 11. Control Flow of Nested-if Statement true inner if false testScore >= 50 ?? testScore >= 50System.out.println System.out.println false studentAge < 10 studentAge < 10 true("You did not ("You did not ??pass"); pass"); System.out.println System.out.println System.out.println System.out.println ("You did aagreat ("You did great ("You did pass"); ("You did pass"); job"); job"); 11
    • 12. Compound Statements• You have to use braces if the <then> or <else> block has multiple statements if (testScore < 70) { Then Block Then Block messageBox.show("You did not pass"); messageBox.show("Try harder next time"); } else { Else Block Else Block messageBox.show("You did pass"); messageBox.show("Keep up the good work"); } 12
    • 13. Style Guideif ( <boolean expression> ) { …} else { Style 1 Style 1 …} if ( <boolean expression> ) { … Style 2 Style 2 } else { … } 13
    • 14. if - else- ifif (score >= 85) { System.out.println(”Grade is A"); Test Grad} else { Score e if (score >= 75) { System.out.println(”Grade is B"); 85 ≤ score A } else { 75 ≤ score < B if (score >= 65) { 85 System.out.println(”Grade is C"); } else { 65 ≤ score < C if (score >= 50) { 75 System.out.println(”Grade is D"); 50 ≤ score < D } else { 65 System.out.println(”Grade is N"); } score < N } 50 }} 14
    • 15. if - else- ifif (score >= 85) { Test Grad System.out.println(”Grade is A"); Score e} else if (score >= 75) { 85 ≤ score A System.out.println(”Grade is B"); 75 ≤ score < B} else if (score >= 65) { 85 System.out.println(”Grade is C"); 65 ≤ score < C} else if (score >= 50) { 75 System.out.println(”Grade is D"); 50 ≤ score < D} else { 65 System.out.println(”Grade is N"); score < N 50} 15
    • 16. Matching else if (x < y) if (x < z) System.out.println("Hello"); else System.out.println("Good bye"); really meansif (x < y) { if (x < z) { System.out.println("Hello"); } else { System.out.println("Good bye"); }} 16
    • 17. Matching else if (x < y) { if (x < z) System.out.println("Hello"); } else { System.out.println("Good bye"); } meansif (x < y) { if (x < z) { System.out.println("Hello"); }} else { System.out.println("Good bye"); 17}
    • 18. Syntax for the switch Statement switch ( <arithmetic expression> ) { <case label 1> : <case body 1> … <case label n> : <case body n> } Arithmetic Expression Arithmetic Expression switch ( fanSpeed ) { case 1:Case CaseLabel System.out.println("Thats low");Label break; case 2: System.out.println("Thats medium"); Case Case break; Body Body case 3: System.out.println("Thats high"); break; } 18
    • 19. The switch Statementchar standing;System.out.println("(F)reshman, (S)ophmore, (J)unior, s(E)nior : ");standing = SavitchIn.readLineNonwhiteChar();switch (standing) { case F: This statement This statement is executed ifif is executed System.out.println("Go to the Wellness Center"); the standing is the standing is break; equal to F. equal to F. case S: System.out.println("Go to the Cox Building"); break; case J: System.out.println("Go to Ashe"); break; case E: This statement This statement is executed ifif is executed System.out.println("Work it out yourself"); the standing is the standing is break; equal to E. equal to E. 19}
    • 20. switch With break Statements true N == N ==switch ( N ) { 11?? xx= 10; = 10; case 1: x = 10; false break; break; break; true N == N == case 2: x = 20; 22?? xx= 20; = 20; break; false break; break; case 3: x = 30; true N == N == break; 33?? xx= 30; = 30;} false break; break; 20
    • 21. The switch Statement with default switch ( <arithmetic expression> ) { <case label 1> : <case body 1> … <case label n> : <case body n> default: <default body> }switch ( binaryDigit ) { case 0: System.out.println("zero"); break; case 1: System.out.println("one"); break; default: System.out.println("Thats not a binary digit"); break; 21}
    • 22. Switch With No break Statements true N == N == xx= 10;switch ( N ) { 11?? = 10; case 1: x = 10; false case 2: x = 20; true N == N == xx= 20; case 3: x = 30; 22?? = 20;} false true N == N == xx= 30; = 30; 33?? false 22
    • 23. Summary• In this class we have discussed about various selection statements 23
    • 24. Assignment• Write a Java program to find whether the given year is leap or not• Write a Java program to find the largest of three numbers• Write a Java program illustrating the functioning of switch statement 24
    • 25. Quiz1.The only relational operation that can be checked in switcha) less thanb) greater thanc) equalityd) all of the above 25
    • 26. Quiz2.Which of the following control statement requires breaka) Ifb) If elsec) Switchd) All of the above 26
    • 27. Quiz3.Default condition is always required in switch statements .[ True/ False] 27
    • 28. Quiz3.Default condition is always required in switch statements .[ True/ False] 28
    • 29. Frequently Asked Questions• Differentiate between switch and if else statements• List the various selection statements of Java• Explain the various selection statements 29
    • 30. swings Struts jdbc hibernate home java previous question papersOCT/NOV-2012 QUESTION PAPER April / May 2012 c-09 October/ November-2011 c-09 April/ May 2011 c-09 April/ May 2011 c-05 Home 30

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