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String, string builder, string buffer
- 2. What is String? • String is non-primitive data type and it is also class which is under java.lang.package. • String is a collection of characters. • String is immutable • Without new keyword we can create object . • It introduced in JDK1.1.
- 3. What is String literals? • String s=“Java”; • SCP is part of Heap memory. “Java” string literal which is stored in String Constant Pool (SCP) SCP
- 4. Why String is immutable? • Strings are constant, values can’t be changed after they are created. • Because java uses the concept of string literal. • Suppose, if one reference variable changes the value of the object, it will be affected to all the reference variables. That is why string objects are immutable in java. • So, String is immutable.
- 5. Example 1: concat() method appends the string at the end so strings are immutable objects.
- 6. Java Programming Java String Constant Pool Heap Memory
- 7. Example 2: So, it assign it to the reference variable it prints Java Programming
- 8. Methods • charAt(), contains(), equals(), equalsIgnoreCase(), toUpperCase, toLowerCase • length(), compareTo, join(), isEmpty(), length(), replaceAll(), replaceFirst() • trim(), index(), lastIndexOf(), toString(),concat(), replace(), equals() • replace(), hashCode(), compareToIgnorCase() • split() • substring()
- 9. Example 3: subString() substring(int start/begin index) substring(int startindex, int endindex) Overloading Returns a new string that is a substring of this string.
- 10. Example 4: equals() Return type is boolean The String equals() method overrides the equals() method of Object class.
- 11. Example 5: equalsIgnoreCase() Return type is boolean
- 13. Example 7: replace() Return type is char, charSequence Replace methods introduced in JDK1.5
- 14. Example 8: split() It returns array of strings computed by splitting this string around matches of the given regular expression. It introduced in JDK 1.4.
- 15. Example 9: split() It returns array of strings computed by splitting this string around matches of the given regular expression. It introduced in JDK 1.4. Overloading
- 16. Example 10: concat() • It returns a string that represents the concatenation of this object's characters followed by the string argument's characters.
- 17. Example 11: contains() Returns a boolean
- 18. Example 12: toString() Returns a hash code
- 19. Example 12: Using toString method to display a value
- 20. Example 13: toUpperCase(), toLowerCase(), chatAt()
- 21. Example 14: length(), join(), isEmpty()
- 22. Example 15: replaceAll(), replaceFirst()
- 27. Methods Name Introduced Version Description Return Type Parameter charAt() 1.0 The char value at the specified index. An index ranges from 0 to length() – 1(length in interface CharSequence) The char value at the specified index of this string. The first char value is at index 0. index - the index of the char value. IsEmpty() 1.6 If it is true, and only if, length() is 0. True if length() is 0, otherwise false No concat() 1.0 Concatenates the specified string to the end of this string.If the length of the argument string is 0, then this String object is returned A string that represents the concatenation of this object's characters followed by the string argument's characters. The String that is concatenated to the end of this String. compareTo() 1.0 The comparison is based on the Unicode value of each character in the strings. The value 0 if the argument string is equal to this string The String to be compared.
- 28. Methods Name Introduced Version Description Return Type Parameter contains() 1.5 True if and only if this string contains the specified sequence of char values. True if this string contains s, false otherwise The sequence to search for. trim() 1.0 a copy of the string, with leading and trailing whitespace omitted. A copy of this string with leading and trailing white space removed, or this string if it has no leading or trailing white space. No equals IgnoreCas e() 1.0 Compares this String to another String, ignoring case considerations true if the argument is not null and it represents an equivalent String ignoring case; false otherwise. The String to compare this String against length() 1.0 The length of this string. The length is equal to the number of Unicode code units in the string. (charAt in interface CharSequence) the length of the sequence of characters represented by this object. No
- 29. Methods Name Introduced Version Description Return Type Parameter Exception replaceAll() 1.4 Replaces each substring of this string that matches the given regular expression with the given replacement. The resulting String. the sequence to search for PatternSyntaxE xception replaceFirst() 1.4 Replaces the first substring of this string that matches the given regular expression with the given replacement. The resulting String. the regular expression to which this string is to be matchedreplacement - the string to be substituted for the first match IndexOutOfBo undsException - compareTo IgnoreCase() 1.2 Compares two strings lexicographically, ignoring case differences. The specified String is greater than, equal to, or less than this String, ignoring case considerations. The String to be compared. No
- 30. Methods Name Introduced Version Description Return Type Parameter Exception toUpperCase() 1.0 Converts all of the characters in this String to upper case using the rules of the default locale. the String, converted to uppercase. No No toLoweCase() 1.0 Converts all of the characters in this String to lower case using the rules of the default locale. the String, converted to lowercase. No No join() 1.8 A string joined with given delimiter. In string join method, delimiter is copied for each elements. Joined string with delimiter. delimiter : char value to be added with each element elements : char value to be attached with delimiter NullPointerExce ption
- 31. Methods Name Introduced Version Description(Overrides a class Object) Return Type Parameter equals() 1.0 Compares this string to the specified object. The result is true if and only if the argument is not null and is a String object that represents the same sequence of characters as this object. True if the given object represents a String equivalent to this string, false otherwise The object to compare this String against hashCode() 1.0 A hash code for this string. A hash code value for this object. No toString() 1.0 The toString method for class Object returns a string consisting of the name of the class of which the object is an instance. This object (which is already a string!) is itself returned. A string representation of the object. No
- 32. Methods Name Introduce d Version Description(Overloading) Return Type Parameter Exception substring() 1.0 Returns a new string that is a substring of this string. The substring begins with the character at the specified index and extends to the end of this string. the specified substring. beginIndex - the beginning index, inclusive. IndexOutOfBoun dsException - substring() 1.0 Returns a new string that is a substring of this string. The substring begins at the specified beginIndex and extends to the character at index endIndex - 1. Thus the length of the substring is endIndex-beginIndex. the specified substring. beginIndex - the beginning index, inclusive. endIndex - the ending index, exclusive. IndexOutOfBoun dsException -
- 33. Methods Name Introduce d Version Description(Overloading) Return Type Parameter Exception replace() 1.0 Returns a new string resulting from replacing all occurrences of oldChar in this string with newChar. A string derived from this string by replacing every occurrence of oldChar with ne wChar. oldChar - the old character.newChar - the new character. No replace() 1.5 Replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence. The resulting String. target - The sequence of char values to be replacedreplaceme nt - The replacement sequence of char values NullPointerExcept ion
- 34. Methods Name Introduced Version Description(Overloading) Return Type Parameter Exception split() 1.4 Splits this string around matches of the given regular expression The array of strings computed by splitting this string around matches of the given regular expression The delimiting regular expression. PatternSyntaxExce ption split() 1.4 Splits this string around matches of the given regular expression. the array of strings computed by splitting this string around matches of the given regular expression. regex - the delimiting regular expressionlimit - the result threshold, as described above PatternSyntaxExce ption -
- 35. Methods Name Introduced Version Description(Overloading) Return Type Parameter Exception index() 1.0 The index within this string of the first occurrence of the specified character. the index of the first occurrence of the character in the character sequence represented by this object a character (Unicode code point). No index() 1.0 “ “ fromIndex - the index to start the search from. No index() 1.0 “ The index of the first occurrence of the specified substring the substring to search for. No index() 1.0 “ “ fromIndex - the index from which to start the search. No
- 36. Methods Name Introduced Version Description(Overloading) Return Type Parameter Exception lastIndex() 1.0 The index within this string of the last occurrence of the specified character. the index of the last occurrence of the character in the character sequence represented by this object a character (Unicode code point). No lastIndex() 1.0 “ “ fromIndex - the index to start the search from. No lastIndex() 1.0 “ The index of the first occurrence of the specified substring the substring to search for. No lastIndex() 1.0 “ “ fromIndex - the index from which to start the search. No
- 37. What is String Buffer? • StringBuffer is mutable String. • Java StringBuffer class is (synchronized )thread-safe i.e. multiple threads cannot access it simultaneously. • So it is safe and will result in an order.
- 38. Why String Buffer is mutable? append() it return many data types Overloading
- 39. Methods • append(), replace(), setCharAt() • insert() • delete() • reverse() • length() • charAt() • deleteChatAt() • setLength()
- 40. Methods Name Introduced Version Description Return Type Parameter Exception delete() 1.2 Removes the characters in a substring of this sequence. This object. start - The beginning index, inclusive.end - The ending index, exclusive. StringIndexOutOf BoundsException deleteCharAt() 1.2 Removes the char at the specified position in this sequence. This sequence is shortened by one char. “ Index of char to remove “ replace() 1.2 Replaces the characters in a substring of this sequence with characters in the specified String. “ start - The beginning index, inclusive.end - The ending index, exclusive.str - String that will replace previous contents. “
- 41. Methods Name Introduced Version Description Return Type Parameter Exception reverse() 1.0.2 Causes this character sequence to be replaced by the reverse of the sequence A reference to this object. No No setLength() 1.0 Sets the length of the character sequence. The sequence is changed to a new character sequence whose length is specified by the argument No The new length IndexOutOfBoun dsException charAt() 1.0 Returns the char value in this sequence at the specified index. the char value at the specified index index - the index of the desired char value. IndexOutOfBoun dsException setCharAt() 1.0 The character at the specified index is set. No index - the index of the character to modify.ch - the new character. IndexOutOfBoun dsException
- 42. Methods Name Introduced Version Description(Overloading) Return Type Parameter Exception append() 1.0 Appends the specified string to this character sequence. A reference to this object. A string. No insert() 1.0 Inserts the string into this character sequence A reference to this object. offset - the offset.str - a string. StringIndexOutOf BoundsException Append() and insert() methods has many types in StringBuffer.
- 43. Example 1: delete(), deleteCharAt()
- 44. Example 2: reverse(), replace()
- 48. What is String Builder? • StringBuilder is mutable String. • The Java StringBuilder class is same as StringBuffer class except that it is non-synchronized (not thread-safe). • It is available since JDK 1.5.
- 49. Methods • append(), replace(), subsequence(), substring(), charAt() , trimToSize() • insert() delete(), capacity(), ensureCapacity(), reverse(), length() • StringBuffer methods is similar to StringBuilder
- 50. Methods Name Introduced Version Description(Overloading) Return Type Parameter Exception subsequence () 1.5 the new character sequence from given start index to exclusive end index value of this sequence. The subSequence(int start, int end) method returns the specified subsequence. The start and end index of a subsequence. IndexOutOfBou ndsException trimToSize( ) 1.5 To reduce the storage used for the character sequence. No No No reverse() 1.5 Causes this character sequence to be replaced by the reverse of the sequence A reference to this object. No No
- 51. Example 1:reverse() Overrides in a String Buffer
- 54. Difference String String Buffer It is immutable It is mutable. String is slow and consumes more memory String is fast and consumes less memory When you concat too many strings because every time it creates new instance. When you cancat strings. 1.0 1.0 Java.lang.package Java.lang.pakage
- 55. Difference StringBuffer String Builder It is immutable It is immutable. It is synchronized i.e. thread safe. It is non-synchronized i.e. not thread safe. It means two threads can't call the methods of StringBuffer simultaneously. It means two threads can call the methods of StringBuilder simultaneously. 1.0 1.5 It is less efficient. It is more efficient.