Strings

A String represents the sequence of characters the easiest way to represent to a sequence of characters in java is by using a character array.

Example:

Char charArray[ ]=new char[4];

CharArray[0]=’J’;

CharArray[1]=’a’;

CharArray[2]=’v’;

CharArray[3]=’a’;

            In java strings are class objects and implemented using two classes, namely, String and StringBuffer. A java string is an instantiated object of the class String class. A java string is not a character array and is not NULL terminated. Strings may be declared as follows:

                        String Stringname;

                        Stringname = new string(“String”);

 Example:

String firstname;

firstname = new String(“Anil”);

these two statements may be combined as follows:

String firstname = new String(“Anil”);

Like arrays, it is possible to get the length of string using the length method of the String class.

int m=firstname.length();

Java strings can be concatenated using the + operator.

 Example;

String fullName =  name1+name2;

String city = ”New”+”Delhi”;

//Program to find substring in java

import java.io.*;

import java.lang.String;

class strings

{

            public static void main(String []args) throws IOException

            {

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

                        String fname,sname;

                        int flag=0;

                        System.out.println("Enter the First Name:");

                        fname=String.valueOf(br.readLine());

                        System.out.println("Enter the Second Name:");

                        sname=String.valueOf(br.readLine());

                        for(int i=0;i<fname.length();i++)

                        {

                                    for(int j=0;j<sname.length();j++)

                                    {

                                                if(fname.charAt(i)!=(sname.charAt(j)))

                                                            continue;

                                                else

                                                            flag++;

                                    }

                        }

                        if(flag!=0)

                                    System.out.println(sname + " is a substring of "+fname);

                        else

                                    System.out.println(sname + " is not a substring of "+fname);

            }

}

Output:

D:\ \programs>javac strings.java

D:\ \programs>java strings

Enter the First Name:

mega star

Enter the Second Name:

mega

mega is a substring of mega star

Commonly used string methods

Method Name	Task Performed
S2=s1.toLowerCase;	Converts string s1 to lowercase
S2=s1.toUpperCase;	Converts string s1 to uppercase
S2=s1.replace(‘x’,’y’);	Replace all x with y
S2=s1.trim();	Remove white spaces
s1.equals(s2)	Returns true is s1=s2
s1.equalsIgnoreCase(s2)	Returns true is s1=s2, ignoring the case
s1.length()	Finds the length of s1
s1.charAt(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.indexOf(‘x’)	Gives the position of first occurrence of x in string s1.