Strings

1. Strings • The String is not a siple data type, it is a class. • The String class represents character strings. All string literals in Java programs, such as "abc", are implemented as instances of this class. • Strings are constant; their values cannot be changed after they are created. String buffers support mutable strings. Because String objects are immutable they can be shared. • For example: • String str = "abc"; • is equivalent to: • char[] data = {'a', 'b', 'c'}; • String str = new String(data); • The String class is final. The String class contains • several methods that allow us to accomplish a variety • of string manipulation tasks. • Eg:test.java • Palindrome.java

2. String is a predefined Java class (in java.lang.String) • a String object encapsulates a sequence of characters • String firstName = "Dave"; • which is equivalent to • String firstName = new String("Dave"); • you can display Strings using System.out.print and System.out.println • System.out.println(firstName); • the '+' operator concatenates two strings (or string and number) together • String str = "foo" + "lish"; • str = str + "ly"; • int age = 19; • System.out.println("Next year, you will be " + (age+1));

3. Difference between Character Array and String Eg:chararraytest.java Chararray.cpp

4. String Methods Method Call Task Performed s2 = s1.toLowerCase() Converts the string S1 to all lowercase s2 = s1.toUpperCase() Converts the string S1 to all uppercase s2 = s1.replace(‘o’,’i’); Replace all appearances of o with i s2 = s1.trim(x); Remove white spaces at the beginning and end of the string S1 S1.equals(S2) Returns ‘true’ if S1 is equals to S2 S1.equalsIgnoreCase(S2) Returns ‘true’ if S1 = S2, ignoring the case of characters S1.length() Gives the length of S1 S1.chartAt (n) Gives nth character of S1 S1.compareTo(S2) Returns negative if S1<S2, positive if S1>S2, and zero if S1 = S2 S1.concat(S2) Concatenates S1 and S2 S1.substring(n) Gives substring starting from nth character S1.substring(n,m) Gives substring starting from nth character up to mth (not including mth) String.valueOf(p) Creates a string object of the parameter p Eg:stringtest.java

5. StringBuffer • It is a peer class of string. While string creates strings of fixed length, string buffer creates strings of flexible length that can be modified in terms of both length and content. • We can insert characters and sub strings in the middle of the string, or append another string to the end.

6. Constructors for StringBuffer 1.StringBuffer() – 16 characters 2.StringBuffer(int size) 3.StringBuffer(String str) Every StringBuffer has two methods 1.length() – no. of characters 2.capacity() - no. of characters, it can contain without being expanded.

7. Commonly Used StringBuffer Methods: S1.setCharAt(n,’x’) : Modifies the nth character to x S1.append(S2) : Appends the strings S2 to S1 at the end S1.insert(n,S2) : Inserts the string S2 at the position n of the string S1 S1.reverse(String s) Eg:stringbuf.java