Tag Archives: String

Java String Project Bases and Decimals

Create a class called BaseMaster (spelled exactly like this)

 

//helper functions

the isNumeric() method returns true if every digit is an integer . It also allows for a single ‘.’ to represent a decimal point.

 

 

example call return value
isNumeric("3.1") true
isNumeric("3.1.1") false
isNumeric("3a") true (assume base 16)
 isNumeric("3D")  true (assume base 16)

To get A+, you need to make base10toOtherBase() support bases 2-10 AND base 16

Java String Loops 2

public int countF(String str)

Description: This method returns the number of times that the letter ‘f’ occurs in str.

Method Call return value/output
countF(“abcdef”) 1
countF(“abcdfef”) 2
countF(“fff”) 3
countF(“xxx”) 0

 

public boolean has2Fs(String str)

Description: This method returns true if str has exactly two occurrences of the letter ‘f’ in it.

Method Call return value/output
has2Fs(“foo”) false
has2Fs(“fofo”) true
has2Fs(“foffo”) false

 

public boolean has2Fs3Gs(String str)

Description: This method returns true if str has exactly two occurrences of the letter ‘f’ in it and 3 occurences ‘g’.

Method Call return value/output
has2Fs3Gs(“foog”) false
has2Fs3Gs(“foggfog”) true
has2Fs3Gs(“foffoggg”) false

public int momOrDad(String str)

Description: This method returns the number of times that the String “mom” or the string “dad” occurs in the parameter str .

Method Call return value/output
momOrDad(“foog”) 0
momOrDad(“momf”) 1
momOrDad(“momdadmo”) 2
momOrDad(“momdadmom”) 3

 

public String threeTimes(String str)

Description: This method returns the String str concatenated with itself three times

Method Call return value/output
threeTimes(“foog”) “foogfoogfoog”
threeTimes(“abc”) “abcabcabc”
threeTimes(“zt”) “ztztzt”
threeTimes(“”) “”

 

public String nTimes(String str, int n)

Description: This method returns the String str concatenated with itself n times

Method Call return value/output
nTimes(“fg” , 2 ) “fgfg”
nTimes(“abc” , 0 ) “”
nTimes(“zt” , 3 ) “ztztzt”
nTimes(“uiz” , 4 ) “uizuizuizuiz”

 

 

public String countMiddleChar(String str)

Precondition: str.length() ≥ 3.

Description: This method returns the number of times the middle letter of str appears in str.

Method Call return value/output
countMiddleChar(“acbcb” ) 2
countMiddleChar(“acbcx” ) 1
countMiddleChar(“bbbbb” ) 5
countMiddleChar(“xytbtzy”) 1

 

 

public int indexOf(String haystack, String needle)

Description: Write your own indexOf() method. Obviously, you cannot make use of the String’s build in indexOf() method. This method returns the index of the first occurrence of needle in haystack . (Full credit if you can get this to work with Strings whose length is greater than 1).

Method Call return value/output
indexOf(“acxb”, “x” ) 2
indexOf(“zazt”, “z” ) 0
indexOf(“tayv”, “g” ) -1
indexOf(“hijklj”, “j” ) 2

If you want the extra credit, then it must also be able to complete the following example calls

Method Call return value/output
indexOf(“acxb”, “cx” ) 1
indexOf(“acxb”, “cxb” ) 1
indexOf(“acxb”, “cxbt” ) -1

 

public int countChars(String str, String chars)

Precondition:The length of chars is less than or equal to the length of str

Description: This method returns the number of times that charsoccurs in String str.

Method Call return value/output
countChars(“momdadmom” , “dad” ) 1
countChars(“foobofoo” , “foo”) 2
countChars(“foobofoofoo” , “foo”) 3
countChars(“foobofoofoo” , “xy” ) 0