Strings in Java

String is generally sequence of a character, in java it is a class. unlike c or c++ at the end of the string the ‘\0’ character is not placed in java.

String is simply defined like

String str = “myString”;

To find  length of a string use length() function.

so str.length() will give me 8 as a string length. like array string also has indexes which starts with 0,

to find character at specific index use charAt(i) function where i is the index of the character.

now lets see the functionality of these 2 String fictions with the help of an example.


public class myString {
public static void main(String[] args)
{
int n=str.length();

String str1="this is a java"; // find character at 3 & length

String str2="hi i am here";// find character at 2  & length

String str3="where are you";// find character at 0 &  length

String str4="this is a demo";// find character at 5 & length

String str5="core java";// find character at 6 & length

System.out.println("Character at 3 of str1 = "+str1.charAt(3) +" | Length is :" + str1.length());
System.out.println("Character at 2 of str2 = "+str2.charAt(2) +" | Length is :" + str2.length());
System.out.println("Character at 0 of str3 = "+str3.charAt(0) +" | Length is :" + str3.length());
System.out.println("Character at 5 of str4 = "+str4.charAt(5) +" | Length is :" + str4.length());
System.out.println("Character at 6 of str5 = "+str5.charAt(6) +" | Length is :" + str5.length());
}
}

output:

Character at 3 of str1 = s | Length is :14
Character at 2 of str2 = | Length is :12
Character at 0 of str3 = w | Length is :13
Character at 5 of str4 = i | Length is :14
Character at 6 of str5 = a | Length is :9

We can convert string to upper case and lower case too using toUpperCase() and toLowerCase() functions. Consider below example.


public class JavaPrograms {
public static void main(String[] args)
{
String str1="this is a java";
String str2="HI I AM VIPULA";
System.out.println("Str1 is:'"+str1+"'");
System.out.println("Str1 in lower case:'"+str1.toUpperCase()+"'");
System.out.println("Str2 is:'"+str2+"'");
System.out.println("Str2 in lower case:'"+str2.toLowerCase()+"'");
}
}

output :
Str1 is:’this is a java’
Str1 in lower case:’THIS IS A JAVA’
Str2 is:’HI I AM VIPULA’
Str2 in lower case:’hi i am vipula’

Another more important function of string is subsring, it has 2 forms

  1. substring(int beginIndex) : it will return a string starting with beginIndex till the end of the string
  2. substring(int beginIndex,int endIndex) : it will return a string starting with beginIndex till the endIndex (practically if you seeyou will observe that in this case the substring starts with the startIndex and it takes till  next (endIndex-startIndex)  characters. e.g. if i am taking str.substring(3,9) the string will start from 3rd index and will take till (9-3=6) i.e. till next 6 characters.)

Let us understand this with example


public class mySubString {
public static void main(String[] args)
{
String str="this is ajava";
System.out.println(str.substring(3));
System.out.println(str.substring(3,9));
}
}

output :

s is ajava
s is a

Lets see one more example. with the help of sub string print below pattern (Make your program generalized in such a way that it should work for any string)

amol
mola
olam
lamo


public class mySubString {
public static void main(String[] args)
{
String str="amol";
for(int i=0;i<str.length();i++)
System.out.println(str.substring(i)+str.substring(0,i));
}
}

output:

amol
mola
olam
lamo

Another important function of String is split. its syntax is str.split(“ch “). it will return an array of a string spitted by the character you specify inside spit. lets understand this with the help of example.


public class SplitFunction {
public static void main(String[] args)
{
String str="this is a java";
String[] strArr = str.split(" "); // split by space.
System.out.println("Given String is '"+str+"'");
System.out.println("There are total "+strArr.length+ " words separeted by space");
for (int i=0;i<strArr.length;i++)
{
System.out.println(strArr[i]);
}
System.out.println("_____________________________");

String str1="12-2-2016";
System.out.println("Given String is '"+str1+"'");
String[] strArr1 = str1.split("-"); // split by space.
System.out.println("There are total "+strArr1.length+ " words separeted by -");
for (int i=0;i<strArr1.length;i++)
{
System.out.println(strArr1[i]);
}
}

}

output:
Given String is ‘this is a java’
There are total 4 words separeted by space
this
is
a
java
_____________________________
Given String is ’12-2-2016′
There are total 3 words separeted by –
12
2
2016

Lets  see one more example on this. consider a string “Hey baby you are so sweet” find out the words in this string ending with ‘y’.(dont use in built function.)


public class SplitExample {
public static void main(String[] args)
{
String str="Hey baby you are so sweet";
String[] strArr=str.split(" ");

for (int i=0; i<strArr.length;i++)
{
if(strArr[i].charAt(strArr[i].length()-1)=='y')
System.out.println(strArr[i]);
}
}
}

output:

Hey
baby


Capgemini interview Question

How will you reverse a string without using in built functions.


public class StringReverse {
public static void main(String[] args)
{
String str="MyString";
String reverse="";
int length = str.length();
for ( int i = length - 1 ; i >= 0 ; i-- )
reverse = reverse + str.charAt(i);
System.out.println("Given string is: "+str);
System.out.println("Reverse of entered string is: "+reverse);
}
}

output:

Given string is: MyString
Reverse of entered string is: gnirtSyM

 


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