Java.lang.String class in Java | Set 2

Java.lang.String class in Java | Set 1 In this article we would be discussing different constructor and methods provided by java.lang.String. Strings in java are immutable. Now lets discuss some of the methods provided by String class. Methods:

1. public int codePointAt(int index) – It takes as parameter a index which must be from 0 to length() – 1. ad returns a character unicode point of a index.
2. public int codePointBefore(int index) – It takes as parameter a index which must be from 0 to length() – 1. and returns a unicode point of a character just before the index .
3. public int codePointCount(int start_index, int end_index) – It takes as parameter start_index and end_index and returns the count of Unicode code points between the range.
4. public CharSequence subSequence(int start_index, int end_index) – This method returns CharSequence which is a subsequence of the String on which this method is invoked. Note: It behaves similarly to subString(int start_index, int end_index), but subString() returns String while subSequence returns CharSequence.
5. public boolean contains(CharSequence char_seq) – It returns true if the given CharSquence is present in the String on which its invoked.
6. public boolean contentEquals(CharSequence char_seq) – It returns true only if the given CharSequence exactly matches the String on which its invoked
7. public boolean endsWith(String suf) – It takes in parameter a String suffix and return true if the String has same suffix.
8. public boolean startsWith(String pre) – It takes in parameter a String prefix and returns true if the String has a same prefix
9. public void getChars(int start, int end, char[] destination, int destination_start) : It takes in four parameters, start and end refers to the range which is to copied to the character array, destination is the character array to be copied to, and destination_start is the starting location of the destination array.
10. public char[] toCharArray() – It converts the entire String to the character array. Note :- getChars provide more flexibility when, a range of characters is to be copied to an existing array or a new array while toCharArray converts the entire string to a new character array.
11. public int hashCode() – It returns hashcode of the given String. There is predefined formula to compute the hashcode of the String:

s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
where,
n - is the length of the String
i - is the ith character of the string

1. public String intern() – It returns the canonical form of the String object on which it is invoked. ” When the intern method is invoked, if the pool already contains a string equal to this String object as determined by the equals(Object) method, then the string from the pool is returned. Otherwise, this String object is added to the pool and a reference to this String object is returned. ” – Java String Documentation.
2. public boolean isEmpty() – It returns true if the length of the String is 0.
3. public static String format(String f, Object… arguments) – Returns the formatted String according to the format specifier f, the arguments should exactly equal to the number of format specifier used . Variation: public static String format(Locale l, String f, Object… arguments)– Returns the formatted String as per Locale used.
4. public boolean matches(String reg_exp) – It returns true if the string matches the regular expression( reg_exp).
5. public boolean regionMatches(int start_OString, String another, int start_AString, int no_of_char) – It returns true if the region of original string starting with index start_OString matches with the region of another string starting with string_AString, and no_of_char refers to the number of character to be compared. Variation : public boolean regionMatches(boolean ignore_case, int start_OString, String another, int start_AString, int no_of_char) – This variation of a method provide flexibility when we want to ignore the case while comparing substring. If the first parameter i.e. ignore_case is true it neglects the case and compares but if it is false it behaves similarly as the first version of the method without ignore_case
6. public String[] split(String reg_exp) – It splits the string around the regular expression and returns a String array. Variation : public String[] split(String reg_exp, int limit) – It splits the string around the regular expression and limit refers to the number of times the reg_exp is applied and it is the length of the resulting array and reg_exp is n is applied only length – 1 times.
7. public static String join(CharSequence de_limiter, CharSequence… elements) – It returns a string which contains all the elements joins by the de_limiter. Variation: public static String join(CharSequence de_limiter, Iterable elements) – It performs the same function but the second parameter is Iterable which makes it flexible to work with different collection classes.
8. public String replaceAll(String reg_exp, String replacement) – It replaces all the Substring of the original string that matches the reg_exp with replacement and returns the modified String.
9. public String replaceFirst(String reg_exp, String replacement) – It replaces the first occurrence of the reg-exp in the original string with the replacement and returns the modified String. Note :- replaceAll and replaceFirst doesn’t changes the original String rather it creates a new string with modification.

For more methods on String refer to String class in java Reference: https://docs.oracle.com/javase/8/docs/api/java/lang/String.html