CS1150 Principles of Computer Science Midterm Review

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1 CS1150 Principles f Cmputer Science Midterm Review Yanyan Zhuang Department f Cmputer Science CS1150 UC. Clrad Springs

2 Office hurs 10/15, Mnday, 12:05 12:50pm 10/17, Wednesday 10:00 10:50am Midterm 10/17, Wednesday, in class 10:50am 12:05pm UC. Clrad Springs

3 Numerical Data Types Name Range Strage Size byte 2 7 t (-128 t 127) 8-bit signed shrt 2 15 t ( t 32767) 16-bit signed int 2 31 t ( t ) 32-bit signed lng 2 63 t bit signed (i.e., t ) flat Negative range: 32-bit IEEE E+38 t -1.4E-45 Psitive range: 1.4E-45 t E+38 duble Negative range: 64-bit IEEE E+308 t -4.9E-324 Reading fr primitive data types: Psitive range: 4.9E-324 t E CS1150 UC. Clrad Springs

4 Integer Divisin +, -, *, /, and % 5 / 2 yields an integer / 2 yields a duble value % 2 yields 1 (the remainder f the divisin) ften called mdularperatin CS1150 UC. Clrad Springs

5 Java Identifiers An identifier A sequence f characters that cnsist f letters, digits, underscres (_), and dllar signs ($) N spaces Must start with a letter, an underscre (_), r a dllar sign ($) It cannt start with a digit An identifier cannt be A reserved wrd true, false, r null An identifier can be f any length CS1150 UC. Clrad Springs

6 Frmatting decimal utput Use DecimalFrmat class DecimalFrmat df = new DecimalFrmat("000.##"); System.ut.println(df.frmat(celsius)); 0: a digit #: a digit, zer shws as absent } 72.5 is shwn as } is shwn as Mre infrmatin alfrmat.html CS1150 UC. Clrad Springs

7 Frmatting decimal utput Use System.ut.frmat (r printf) System.ut.frmat("the %s jumped ver the %s, %d times", "cw", "mn", 2); } the cw jumped ver the mn, 2 times System.ut.frmat("%.1f", ); } 10.3 // ne decimal pint System.ut.frmat("%.2f", ); } // tw decimal pints System.ut.frmat("%8.2f", ); } // Eight-wide, twdecimal pints CS1150 UC. Clrad Springs

8 Variables and Cnstants Variable Decimal numbers: t indicate flat/duble, use suffix f/d } Leaving ff the suffix, the number defaults t a duble flat flatvalue = 71.71f; } If leave ff f wuld get errr: cannt cnvert duble t flat duble dublevalue = d; } If yu left ff the d there is n issue Use duble (safe!) CS1150 UC. Clrad Springs

9 Variables and Cnstants Cnstant Used t stre a value that will NEVER change Cnstants fllw certain rules } Must have a name (a meaningful name, like variables) } Name cnstants with all uppercase letters (Java cnventin) } Declared using the keywrd final Example: final duble PI = ; CS1150 UC. Clrad Springs

10 Data Casting When yu explicitly tell Java t cnvert a variable frm ne data type t anther type Think f data types as cups f different sizes } Can put the cntents f a smaller variable (cup) int a larger variable (cup) } Cannt put the cntents frm a larger variable (cup) int a smaller variable (cup), withut lsing infrmatin } Cheat sheet: int (32 bits), duble (64 bits) CS1150 UC. Clrad Springs

11 Cnversin Rules When perfrming a binary peratin invlving tw perands f different types, Java autmatically cnverts the perand based n the fllwing rules: 1. If ne f the perands is duble, the ther is cnverted int duble. 2. Otherwise, if ne f the perands is flat, the ther is cnverted int flat. 3. Otherwise, if ne f the perands is lng, the ther is cnverted int lng. 4. Otherwise, bth perands are cnverted int int. 11

12 Augmented Assignment Operatrs +, -, *, / and % peratrs Each can be cmbined with the assignment peratr (=) a = a + 1; => a += 1; Same as -=, *=, /= and %= CS1150 UC. Clrad Springs

13 Increment and Decrement Operatrs Increment: ++ Decrement: -- Operatr can be placed befre r after variables (pstfix) int i = 1, j = 3; i++; // Same as i = i + 1; i will becme 2 j--; // Same as j = j 1; j will becme 2 Alternatively (prefix) int i = 1, j = 3; ++i; // Same as i = i + 1; i will becme 2 --j; // Same as j = j 1; j will becme 2 Placement f prefix r pstfix cause different results when in expressins CS4500/5500 UC. Clrad Springs

14 Order f Operatrs (Sectin 3.15) Anything in parentheses expr++ expr-- (pstfix) expr --expr (unary plus/minus, prefix) (type) (Casting)! (nt) * / % (multiplicatin, divisin, remainder) + - (binary additin, subtractin) < <= > >= (relatinal peratrs) ==!= (equality) ^ (exclusive r) && (and) (r) = += -= *= /= %= (assignment, augmented assignment) CS1150 UC. Clrad Springs

15 If statement The else clause matches the mst recent if clause An else" always belngs with the mst recent if CS1150 UC. Clrad Springs

16 If statement T frce the else clause t match the first if clause, must add a pair f braces: int i = 1, j = 2, k = 3; if (i > j) { } if (i > k) else System.ut.println("A"); System.ut.println("B"); CS1150 UC. Clrad Springs

17 switch Statement Ntes switch expressin Must evaluate t a value f type char, byte, shrt, int } switch (x > 1) // Nt allwed - evaluates t a blean value } switch (x == 2) // Nt allwed - anther blean expressin CS4500/5500 UC. Clrad Springs

18 switch Statement Ntes Case values Are cnstants expressins Cannt cntain variables } case 0: system.ut.println("..."); // valid } case (x+1): system.ut.println("..."); // nt valid Thugh this is valid way t write the cases int value = 3; switch (value) { case 1:case 2:case 3: System.ut.println("case 1, 2, and 3"); break; case 4: System.ut.println("case 4"); break; default: System.ut.println("default"); } CS4500/5500 UC. Clrad Springs

19 switch Statement Ntes break statement int day = 3; switch (day) { case 1: case 2: case 3: case 4: case 5: System.ut.println("Weekday"); break; case 0: case 6: System.ut.println("Weekend"); } CS4500/5500 UC. Clrad Springs

20 Cnditinal Expressins Shrtcut way t write a tw-way if statement (if-else) Cnsists f the symbls? and : (aka the "ternary" peratr) result = expressin? value1 : value2 } expressin can be either a blean value r a statement that evaluates t a blean value } The cnditinal "expressin" is evaluated } If the expressin is true, value1 is returned } If the expressin is false, value2 is returned CS1150 UC. Clrad Springs

21 Rules fr While/D..while Lps The lp cnditin must be a blean expressin Blean expressin must be in parentheses Blean expressins are frmed using relatinal r lgical peratrs Lp cnditin Usually a statement befre the while lp "initializes" the lp cnditin t true Sme statement within the lp bdy eventually change the cnditin t false If the cnditin is never changed t false, the prgram is frever in the lp This is called an "infinite lp" Curly braces are nt necessary if nly ne statement in lp But best practice is t always include curly braces UC. Clrad Springs

22 Rules f fr lps The cntrl structure f the fr-lp needs t be in parentheses fr (i=0; i<= 2; i++) { statements; } The lp cnditin (i <= 2) must be a blean expressin The cntrl variable (i): nt recmmended t be changed within the fr-lp bdy Curly braces are nt necessary if nly ne statement in lp Best practice is t always include curly braces UC. Clrad Springs

23 Using break and cntinue Break in lps Used "break" in switch statements t end a case Can be used in a lp t terminate a lp Breaks ut f lp Cntinue in lps Used t end current iteratin f lp Prgram cntrl ges t end f lp bdy UC. Clrad Springs

24 Nte Yu may declare the cntrl variable utside/within the fr-lp fr (int j = 0; j <= 5; j++) { } } System.ut.println ("Fr lp iteratin = " + j); int j; fr (j = 0; j <= 5; j++) { System.ut.println ("Fr lp iteratin = " + j); Nte n variable scpe (the area a variable can be referenced) Declaring cntrl variable befre the fr lp cause its scpe t be inside and utside frlp Declaring the cntrl variable in the fr-lp causes its scpe t be nly inside the fr lp } If I tried t use the variable j utside the fr-lp - errr UC. Clrad Springs

25 Nte Mistakes t avid Infinite lps Off-by-ne errr Nested lps Knw hw t trace them UC. Clrad Springs

26 The Math Class Class cnstants: PI ( ) E ( base f natual lg) Class methds: Trignmetric Methds Expnent Methds Runding Methds min, max, abs, and randm Methds 26

27 Randm Numbers Math.randm() Hw t generate a randm integer between [lwer, upper)? } Example: int lwer=100, upper=120; } randmduble = Math.randm(); // [0.0, 1.0) } randmduble = randmduble * (upper-lwer); // [0.0, 20.0) } randmduble = lwer + randmduble; // [100.0, 120.0) } randmint = (int) randmduble; // cast duble à int Or in ne step } randmint = (int) (lwer + Math.randm() * (upper-lwer)); UC. Clrad Springs

28 Character Data Type Values: ne single character Use single qute t represent a character (dubles qutes are fr Strings) } char middleinitial = 'M'; } char numcharacter = '4'; // Assigns digit character 4 t numcharacter } System.ut.println(numCharacter); // Displays 4 Placing a character in it is n lnger a char: it is a String } char middleinitial = "M"; // Errr - cannt cnvert String t char CS1150 UC. Clrad Springs

29 ASCII Cde fr Cmmnly Used Characters Characters Cde Value in Decimal Unicde Value '0' t '9' 48 t 57 \u0030 t \u0039 'A' t 'Z' 65 t 90 \u0041 t \u005a 'a' t 'z' 97 t 122 \u0061 t \u007a Mre infrmatin: 29

30 Casting between char and Numeric Types int i = 'a'; // Same as int i = (int)'a'; System.ut.println ( i = " + i); // i = 97 all numeric peratrs can be applied t the char perands char c = 97; // Same as char c = (char)97; System.ut.println ("c = " + c); // c = a Increment and decrement can be used n char variables t get the next r preceding ASCII/Unicde character. char ch = 'a'; System.ut.println(++ch); //shws character b 30

31 Cmparing and Testing Characters if (ch >= 'A' && ch <= 'Z') System.ut.println(ch + " is an uppercase letter"); else if (ch >= 'a' && ch <= 'z') System.ut.println(ch + " is a lwercase letter"); else if (ch >= '0' && ch <= '9') System.ut.println(ch + " is a numeric character"); all numeric peratrs can be applied t the char perands 31

32 Hw t generate a randm character? A randm character between any tw characters ch1 and ch2 with ch1 < ch2 can be generated as: (char)(ch1 + Math.randm() * (ch2 ch1 + 1)) Example: randm upper case letter } (char)( A + Math.randm() * ( Z A + 1)) Example: randm numeric character } (char)( 0 + Math.randm() * ( )) UC. Clrad Springs

33 Hw t cnvert a numeric int character t its int value? Cnverting 0 t 0, etc. Example: hw t cnvert 0 t 0? 0-0 is is is 2... UC. Clrad Springs

34 The String Type A char is in single qutes and a String is in duble qutes char middleinitial = "M"; // Errr - can t cnvert String t char char middleinitial = 'M'; // Crrect string studentname = "Max" // Errr - uppercase "String" String studentname = 'Max'; // Errr - duble qutes String studentname = "Max"; // Crrect CS1150 UC. Clrad Springs

35 Strings and chars String methds (length, get char frm String) Read Strings/chars frm cnsle Cncatenate/cmpare Strings Cnverting between numbers and Strings Finding substrings Frmatting utput (%s, %d etc.) UC. Clrad Springs

CS1150 Principles of Computer Science Final Review

CS1150 Principles of Computer Science Final Review CS1150 Principles f Cmputer Science Final Review Yanyan Zhuang Department f Cmputer Science http://www.cs.uccs.edu/~yzhuang CS1150 UC. Clrad Springs Numerical Data Types Name Range Strage Size byte 2 7