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70 Java String Exercises.

How many of these can you do in two 1-hour sessions?

If at first you cannot see the answer quickly, move to the next problem.

Implement the tests suggested by the Sample Output and write the method that makes the tests succeed.


1. Write a Java program to get the character at the given index within the String.  

Sample Output:

Original String = Java Exercises!                                                                             
The character at position 0 is J                                                                              
The character at position 10 is i 
 
2. Write a Java program to get the character (Unicode code point) at the given index (1 and 9) within the String.

Sample Output:

Original String : w3resource.com                                                                              
Character(unicode point) = 51                                                                                 
Character(unicode point) = 101 
 

3. Write a Java program to get the character (Unicode code point) BEFORE the specified index (1 and 9) within the String.

Sample Output:

Original String : w3resource.com                                                                              
Character(unicode point) = 119                                                                                
Character(unicode point) = 99
 

4. Write a java program to count a number of Unicode code points in the specified text range of a String.  

Sample Output:

Original String : w3rsource.com                                                                               
Codepoint count = 9
 

5. Write a java program to compare two strings lexicographically.  

Sample Output:

String 1: This is Exercise 1                                                                                  
String 2: This is Exercise 2                                                                                  
"This is Exercise 1" is less than "This is Exercise 2" 
 

6. Write a java program to compare two strings lexicographically, ignoring case differences.  

Sample Output:

String 1: This is exercise 1                                                                                  
String 2: This is Exercise 1                                                                                  
"This is exercise 1" is equal to "This is Exercise 1"
 

7. Write a Java program to concatenate a given string to the end of another string.  

Sample Output:

String 1: PHP Exercises and                                                                                   
String 2: Python Exercises                                                                                    
The concatenated string: PHP Exercises and Python Exercises
 

8. Write a Java program to test if a given string contains the specified sequence of char values.  

Sample Output:

Original String: PHP Exercises and Python Exercises                                                           
Specified sequence of char values: and                                                                        
true 
 

9. Write a Java program to compare a given string to the specified character sequence.  

Sample Output:

Comparing example.com and example.com: true                                                                   
Comparing Example.com and example.com: false
 

10. Write a Java program to compare a given string to the specified string buffer.  

Sample Output:

Comparing example.com and example.com: true                                                                   
Comparing Example.com and example.com: false 
 

11. Write a Java program to create a new String object with the contents of a character array.  

Sample Output:

The book contains 234 pages.
 

12. Write a Java program to check whether a given string ends with the contents of another string.  

Sample Output:

"Python Exercises" ends with "se"? false                                                                      
"Python Exercise" ends with "se"? true
 

13. Write a Java program to check whether two String objects contain the same data.  

Sample Output:

"Stephen Edwin King" equals "Walter Winchell"? false                                                          
"Stephen Edwin King" equals "Mike Royko"? false
 

14. Write a Java program to compare a given string to another string, ignoring case considerations.  

Sample Output:

"Stephen Edwin King" equals "Walter Winchell"? false                                                          
"Stephen Edwin King" equals "stephen edwin king"? true 
 

15. Write a java program to print current date and time in the specified format.  

Sample Output:

Current Date and Time :                                                                                       
June 19, 2017                                                                                                 
3:13 pm 
N.B. : The current date and time will change according to your system date and time.
 

16. Write a Java program to get the contents of a given string as a byte array.  

Sample Output:

The new String equals This is a sample String.
 

17. Write a Java program to get the contents of a given string as a character array.  

Sample Output:

The char array equals "[C@2a139a55"
 

18. Write a Java program to create a unique identifier of a given string.  

Sample Output:

The hash for Python Exercises. is 863132599 
 

19. Write a Java program to get the index of all the characters of the alphabet.  

Sample Output:

a  b c  d e  f  g h i  j                                                                                     
=========================                                                                                     
36 10 7 40 2 16 42 1 6 20                                                                                     
                                                                                                   
k  l  m  n  o  p q  r  s  t                                                                                   
===========================                                                                                   
8 35 22 14 12 23 4 11 24 31                                                                                   

u  v  w  x  y  z                                                                                              
================                                                                                              
5 27 13 18 38 37
Sample string of all alphabet: "The quick brown fox jumps over the lazy dog."

 

20. Write a Java program to get the canonical representation of the string object.  

Sample Output:

str1 == str2? false                                                                                           
str1 == str3? true
 

21. Write a Java program to get the last index of a string within a string.  

Sample Output:

 a  b c  d  e  f  g  h i  j                                                                                   
===========================                                                                                   
36 10 7 40 33 16 42 32 6 20                                                                                   
                                                                                                              
k  l  m  n  o  p q  r  s  t                                                                                   
===========================                                                                                   
8 35 22 14 41 23 4 29 24 31                                                                                   
                                                                                                              
 u  v  w  x  y  z                                                                                             
=================                                                                                             
21 27 13 18 38 37
Sample string of all alphabet: "The quick brown fox jumps over the lazy dog."

 

22. Write a java program to get the length of a given string.  

Sample Output:

The string length of 'example.com' is: 11
 

23. Write a Java program to find whether a region in the current string matches a region in another string.  

Sample Output:

str1[0 - 7] == str2[28 - 35]? true                                                                            
str1[9 - 15] == str2[9 - 15]? false 
 

24. Write a Java program to replace all the 'd' characters with 'f' characters.  

Sample Output:

Original string: The quick brown fox jumps over the lazy dog.                                                 
New String: The quick brown fox jumps over the lazy fog.
 

25. Write a Java program to replace each substring of a given string that matches the given regular expression with the given replacement.  

Sample string : "The quick brown fox jumps over the lazy dog."

In the above string replace all the fox with cat.

Sample Output:

Original string: The quick brown fox jumps over the lazy dog.                                                 
New String: The quick brown cat jumps over the lazy dog.         
 

26. Write a Java program to check whether a given string starts with the contents of another string.  

Sample Output:

Red is favorite color. starts with Red? true                                                                  
Orange is also my favorite color. starts with Red? false
 

27. Write a Java program to get a substring of a given string between two specified positions.  

Sample Output:

old = The quick brown fox jumps over the lazy dog.                                                            
new = brown fox jumps
 

28. Write a Java program to create a character array containing the contents of a string.  

Sample Output:

Java Exercises.
 

29. Write a Java program to convert all the characters in a string to lowercase.  

Sample Output:

Original String: The Quick BroWn FoX!                                                                         
String in lowercase: the quick brown fox!
 

30. Write a Java program to convert all the characters in a string to uppercase.  

Sample Output:

Original String: The Quick BroWn FoX!                                                                         
String in uppercase: THE QUICK BROWN FOX!  
 

31. Write a Java program to trim any leading or trailing whitespace from a given string.  

Sample Output:

Original String:  Java Exercises                                                                              
New String: Java Exercises
 

32. Write a Java program to find longest Palindromic Substring within a string.  

Sample Output:

The given string is: thequickbrownfoxxofnworbquickthe
The longest palindrome substring in the giv
en string is; brownfoxxofnworb
The length of the palindromic substring is: 16
 

33. Write a Java program to find all interleavings of given strings.  

Sample Output:

The given strings are: WX  YZ
The interleavings strings are: 
YWZX
WYZX
YWXZ
WXYZ
YZWX
WYXZ
 

34. Write a Java program to find the second most frequent character in a given string.  

Sample Output:

The given string is: successes
The second most frequent char in the string is: c
 

35. Write a Java program to print all permutations of a given string with repetition.  

Sample Output:

The given string is: PQR
The permuted strings are:
PPP
PPQ
PPR
...
RRP
RRQ
RRR
 

36. Write a Java program to check whether two strings are interliving of a given string. Assuming that the unique characters in both strings.  

Sample Output:

The given string is: PMQNO
The interleaving strings are MNO and PQ
The given string is interleaving: true

The given string is: PNQMO
The interleaving strings are MNO and PQ
The given string is interleaving: false
 

37. Write a Java program to find Length of the longest substring without repeating characters.  

Sample Output:

Input String : pickoutthelongestsubstring
The longest substring : [u, b, s, t, r, i, n, g]
The longest Substring Length : 8
 

38. Write a Java program to print after removing duplicates from a given string.  

Sample Output:

The given string is: w3resource
After removing duplicates characters the new string is: w3resouc
 

39. Write a Java program to find first non repeating character in a string.  

Sample Output:

The given string is: gibblegabbler
The first non repeated character in String is: i
 

40. Write a Java program to divide a string in n equal parts.  

Sample Output:

The given string is: abcdefghijklmnopqrstuvwxy
The string divided into 5 parts and they are: 

abcde
fghij
klmno
pqrst
uvwxy
 

41. Write a Java program to remove duplicate characters from a given string presents in another given string.  

Sample Output:

The given string is: the quick brown fox
The given mask string is: queen

The new string is: 
th ick brow fox
 

42. Write a Java program to print list items containing all characters of a given word.  

Sample Output:

The given strings are: rabbit   bribe   dog   
The given word is: bib 

The strings containing all the letters of the given word are: 
rabbit
bribe
 

43. Write a Java program to find the maximum occurring character in a string.  

Sample Output:

The given string is: test string
Max occurring character in the given string is: t
 

44. Write a Java program to reverse a string using recursion.  

Sample Output:

The given string is: The quick brown fox jumps
The string in reverse order is:
spmuj xof nworb kciuq ehT
 

45. Write a Java program to reverse words in a given string.  

Sample Output:

The given string is: Reverse words in a given string
The new string after reversed the words: string given a in words Reverse
 

46. Write a Java program to reverse every word in a string using methods.  

Sample Output:

The given string is: This is a test string
The string reversed word by word is: 
sihT si a tset gnirts
 

47. Write a Java program to rearrange a string so that all same characters become d distance away.  

Sample Output:

The given string is: accessories
The string after arrange newly is: 
secrsecisao
 

48. Write a Java program to remove "b" and "ac" from a given string.  

Sample Output:

The given string is: abrambabasc
After removing the new string is: aramaasc
 

49. Write a Java program to find first non-repeating character from a stream of characters.  

Sample Output:

String: godisgood
Reading: g
The first non-repeating character so far is:  g
Reading: o
The first non-repeating character so far is:  g
Reading: d
The first non-repeating character so far is:  g
Reading: i
The first non-repeating character so far is:  g
Reading: s
The first non-repeating character so far is:  g
Reading: g
The first non-repeating character so far is:  o
Reading: o
The first non-repeating character so far is:  d
Reading: o
The first non-repeating character so far is:  d
Reading: d
The first non-repeating character so far is:  i
 

50. Write a Java program to find lexicographic rank of a given string.  

Sample Output:

The Given String is: BDCA
The Lexicographic rank of the given string is: 12
N.B.: Total possible permutations of BDCA are(lexicographic order) :
ABCD ABDC ACBD ACDB ADBC ADCB BACD BADC BCAD BCDA BDAC BDCA
1   2   3   4   5   6   7   8   9   10   11   12 
The BDCA appear in 12 position of permutation (lexicographic order).

 

51. Write a Java program to count and print all the duplicates in the input string.  

Sample Output:

The given string is: w3resource
The duplicate characters and counts are: 
e  appears  2  times
r  appears  2  times
 

52. Write a Java program to check if two given strings are rotations of each other.  

Sample Output:

The given strings are: ABACD  and  CDABA

The concatination of 1st string twice is: ABACDABACD
The 2nd string CDABA  exists in the new string.

Strings are rotations of each other
 

53. Write a Java program to match two strings where one string contains wildcard characters.  

Sample Output:

The given string is: abcdhgh
The given pattern string is: abc*d?*
The given pattern is matching.
 

54. Write a Java program to find the smallest window in a string containing all characters of another string.  

Sample Output:

The given string is: welcome to w3resource
Characters to find in the main sring are: tower
The smallest window which contains the finding characters is : to w3re
 

55. Write a Java program to remove all adjacent duplicates recursively from a given string.  

Sample Output:

The given string is: aabaarbarccrabmq
The new string after removing all adjacent duplicates is:
brmq
 

56. Write a Java program to append two given strings such that, if the concatenation creates a double characters then omit one of the characters.  

Sample Output:

The given strings are: food  and  door
The string after concatination are: foodoor
 

57. Write a Java program to return a new string where the last two characters of a given string, if present, are swapped.  

Sample Output:

The given strings is: string
The string after swap last two characters are: strign
 

58. Write a Java program to read a string and return true if it ends in "ng".  

Sample Output:

The given strings is: string
The string containing ng at last: true

The given strings is: strign
The string containing ng at last: false
 

59. Write a Java program to read a string,if the string begins with "red" or "black" return that color string, otherwise return the empty string.  

Sample Output:

The given strings is: blacksea
The string begins with the color: black
 

60. Write a Java program to read two strings append them together and return the result. If the strings are different lengths, omit chars from the beginning of longer string and make them equal length.  

Sample Output:

The given strings is: Welcome and home
The new string is: comehome
 

61. Write a Java program to read a string and an int n, return a string made of the first and last n characters from the string.  

Sample Output:

The given strings is: Welcome
The given numbers is: 3
The new string is: Welome
 

62. Write a Java program to read a string and return true if "good" appears starting at index 0 or 1 in the given string. 

Sample Output:

The given strings is: goodboy
The 'good' appear in the string is: true
 

63. Write a Java program to return true from a given string if the first two characters in the string also appear at the end.  

Sample Output:

The given strings is: educated
The first two characters appear in the last is: true
 

64. Write a Java program to read a string and if a substring of length two appears at both its beginning and end, return a string without the substring at the beginning otherwise, return the original string unchanged.  

Sample Output:

The given strings is: educated
The new string is: ucated
 

65. Write a Java program to read a string and if the first or last characters are 't', return the string without those 't' otherwise return the string unchanged.  

Sample Output:

The given strings is: testcricket
The new string is: estcricke
 

66. Write a Java program to read a string and return the string without the first two characters.Except keep the first char if it is 'g' and keep the second char if it is 'h'.  

Sample Output:

The given strings is: goat
The new string is: gat

he given strings is: photo
The new string is: hoto

The given strings is: ghost
The new string is: ghost
 

67. Write a Java program to read a string and if one or both of the first tow characters is 'x', return without those 'x',otherwise return the string unchanged.  

Sample Output:

The given strings is: oocyte
The new string is: cyte

The given strings is: boat
The new string is: bat

The given strings is: own
The new string is: wn
 

68. Write a Java program to read a string and returns after remove the # and its immediate left and right characters.  

Sample Output:

The given strings is: test#string
The new string is: testring

The given strings is: test##string
The new string is: testring

The given strings is: test#the#string
The new string is: teshtring
 

69. Write a Java program to return the substring that is between the first and last appearance of the substring 'toast' in the given string,or return the empty string if substirng 'toast' does not exists.  

Sample Output:

The given strings is: sweettoastbuttertoast
The new string is: butter
 
 
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