CS 110 Notes Basics II More on Assignment operators o Variable expression o Evaluate the expression and then store the result as the value of variable o Compound operators Variable compound operator expression a 5 a a 5 a 5 a a 5 a 5 c a a 5 c o Page 111 20 3rd edition Page 99 20 4th edition Rewrite the assignment statement using a compound operator a x 2 x b x x y 2 c sum sum num do d e for non collected homework Increment Decrement Operators o a a 1 o a a 1 o common often used operation o built in machine instructions to cover these inc dec o a a a 1 o a a a 1 o syntax allows a or a a or a o can use it within an expression a b a b these two are not equivalent never or except in a stand alone statement Math Library o Collection of methods for all elementary math functions o Such as pow sqrt floor ceil abs sin cos etc o To use qualify the method with Math o qualifying operator member access operator Copyright C Tanner 2010 1 CS 110 Notes Basics II Math pow x y In the math library use the method called pow The qualifies that pow can be found in the Math library System out print the print function for the out buffer from System class Sample Programs Invest java Standard java Circlem java Random Numbers o Often times need to generate random numbers to be used within our programs o Math library has a function called random o Pseudo random Number generator o Math random Returns a number between 0 0 and 1 0 To create a two digit random number 0 99 Math random 100 To create a 1 digit random number 0 9 Math random 10 To create a number between 1 y Math random y 1 Sample Program Roulette java String Data Type o Sequence of 0 or more characters o Enclosed in cs 110 I hate Programming o Index Characters position within the string 1st character has index 0 CS 110 C index 0 S index 1 index 2 1 index 3 1 index 4 0 index 5 o Length of characters in the string CS 110 length 6 I hate Programming length 18 String s the blue screen of death int len len s length o len 24 o First character index 0 o Last character index of length 1 Copyright C Tanner 2010 2 CS 110 Notes Basics II o Operations concatenate String wholeName last first wholeName first last charAt index returns the character at the index charAt 0 returns the first character charAt i returns the ith character s charAt 0 references the first character s charAt s length 1 references the last character substring b e returns the characters from the b index to e index b beginning index e ending index leave off e then it takes to the end of the string String str CS 110 str substring 0 1 CS str substring 1 S 110 indexOf returns the position of the first it finds in the string String str CS 110 int x str indexOf x 2 toLowerCase converts each character to its lower case equivalent String str I HATE PROGRAMMING str toLowerCase I hate programming to change just a character o Character toLowercase A a toUpperCase converts each character to its upper case equivalent replace source target replaces the source string with the target string String str CS 110 str replace 110 111 CS 111 Sample Programs Piglatin java previous outside lab assignments Homework not to be turned in page 171 6 rd Edition Page 158 6 4th edition Formatting Double values on Printing o Usually displays many decimal digits o Can be formatted using String format command o double netPay o String formattedNetPay String format 2f netPay o f the specifies the number of decimal places Copyright C Tanner 2010 3 CS 110 Notes Basics II o 0f integer result o Page 152 154 3rd Edition Page 139 142 4th edition for more info Copyright C Tanner 2010 4