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 This article is contributed by Sumit Ghosh. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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