Strings
String Methods
| Useful Method and Description |
|---|
charAt(int index)Returns the char value at the specified index. |
compareTo(String anotherString)Compares two strings lexicographically. |
concat(String str)Concatenates the specified string to the end of this string. |
contains(CharSequence s)Returns true if and only if this string contains the specified sequence of char values. |
equals(Object anObject)Compares this string to the specified object. |
getBytes()Encodes this String into a sequence of bytes using the platform’s default charset, storing the result into a new byte array. |
getBytes(String charsetName)Encodes this String into a sequence of bytes using the named charset, storing the result into a new byte array. |
hashCode()Returns a hash code for this string. |
indexOf(int ch)Returns the index within this string of the first occurrence of the specified character. |
indexOf(String str)Returns the index within this string of the first occurrence of the specified substring. |
isEmpty()Returns true if, and only if, length() is 0. |
length()Returns the length of this string. |
matches(String regex)Tells whether or not this string matches the given regular expression. |
regionMatches(int toffset, String other, int ooffset, int len)Tests if two string regions are equal. |
replace(CharSequence target, CharSequence replacement)Replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence. |
split(String regex)Splits this string around matches of the given regular expression. |
startsWith(String prefix)Tests if this string starts with the specified prefix. |
substring(int beginIndex)Returns a string that is a substring of this string. |
substring(int beginIndex, int endIndex)Returns a string that is a substring of this string. |
toCharArray()Converts this string to a new character array. |
toLowerCase()Converts all of the characters in this String to lower case using the rules of the default locale. |
toString()This object (which is already a string!) is itself returned. |
toUpperCase()Converts all of the characters in this String to upper case using the rules of the default locale. |
trim()Returns a string whose value is this string, with any leading and trailing whitespace removed. |
valueOf(char c)Returns the string representation of the char argument. |
valueOf(char[] data)Returns the string representation of the char array argument. |
valueOf(double d)Returns the string representation of the double argument. |
valueOf(Object obj)Returns the string representation of the Object argument. |
Questions
Question – 1: Check if the given String has no duplicate characters
private static boolean checkIsUniqueModified(String isUnique) {
boolean[] unique = new boolean[128];
char[] array = isUnique.toCharArray();
for (int i = 0; i < array.length; i++) {
char value = isUnique.charAt(i);
if (unique[value]) {
return false;
} else {
unique[value] = true;
}
}
return true;
}
Question – 2: Check if the given String Can be compressed and expressed in shorter form
private static String compression(String input) {
char[] array = input.toCharArray();
StringBuilder builder = new StringBuilder();
int count = 1;
for (int i = 0; i < array.length; i++) {
if (i < array.length -1 && array[i] == array[i + 1]) {
count ++;
continue;
}
builder.append(array[i]).append(count);
count = 1;
}
return new String(builder);
}
Question – 3: Check if the given String is a palindrome permutation
public static void main(String[] args) {
String input = "aabbddaa";
Map<Integer, Integer> map = new HashMap<>();
char[] array = input.trim().toLowerCase().toCharArray();
for (int i = 0; i < array.length; i++) {
int sum = 0;
if (map.get(Integer.valueOf(array[i])) != null) {
sum = map.get(Integer.valueOf(array[i]));
}
map.put(Integer.valueOf(array[i]), sum +1);
}
long count = map.values().stream().filter((i) -> {
if(i % 2 == 0) {
return false;
}
return true;
}).count();
if (count > 1) {
System.out.println(" Not Palliandrome");
} else {
System.out.println("Palliandrome");
}
}
Question – 4: Check if the input String is a permutation of the given String
private static boolean checkPermutation(String str1, String str2) {
char[] str1Array = str1.toCharArray();
Arrays.sort(str1Array);
char[] str2Array = str2.toCharArray();
Arrays.sort(str2Array);
return new String(str1Array).equals(new String(str2Array));
}
Question – 5: Check if the input String is a rotation of the given String
private static boolean isStringRotation(String word1, String word2) {
String combined = word1 + word1;
return combined.contains(word2);
}
