Strings In Java

Strings In Java

String: String is a collection of characters (OR) It can also be defined as a character array. String is a predefined class in java which contains methods variables . These are immutable in nature (Once an object is created cant be changed).

Syntax:

Initialization of String:

String variable[]={'char1','char2','char3'.......};

 String object="value";

Example:

String st={'v','o','i','d'};

 String obj="void";

Declaration of String:

String can be declared in many ways as follows :

 String str[];

 Example:

 String str[];

Predefined Methods In String Class 

1. length():  It is used to return the length of a string . The return value of length method is an integer.

Syntax:

object.length();

2. charAt(int position): It is used to return a character at a specified of position in the parameter. Position is a integer parameter which will be considered as index of the String.

Syntax:

object.charAt(integer value);

 3.equals(String variable): It is used to return a boolean value . if both the strings are equal and are of same case then it returns true otherwise false.

 Syntax:

 object.equals(string object);

 4.equalsIgnoreCase(String variable): It is used to return a boolean value without checking the case values of the string . If both the strings are equal then ot returns true otherwise falls.

 Syntax:

 object.equalsIgnoreCase(String object2);

 5.toUpper(): It is used to convert the string to upper case letters . If the given String is already in upper case then it ignores that string or a character.

 Syntax:

 objet.toUpper();

6.toLower(): It is used to convert the string to Lower case letters . If the given String is already in Lower case then it ignores that string or a character.

 Syntax:
objet.toUpper();

 7. concat(String Variable): It is used for combining two Strings together forming into a single String. The return type of concat method is also a String.
Syntax:

 object.concat(object2);

 8.trim(): It is used to remove the spaces present before the String and after the String. The return type of trim method is String.

 Syntax:

 object.trim();

 9.compareTo(String variable): It is used to compare the String lexicographically  , It returns positive negative or 0 . if first String is greater than the second String it returns positive value . if first String is lesser than the second String it returns negative value . If both are equal then returns 0. 

 Syntax:

 object.compareTo(object2);

 10.compareToIgnoreCase(String variable); It is used to compare the String lexicographically  , It returns positive negative or 0 . if first String is greater than the second String it returns positive value . if first String is lesser than the second String it returns negative value . If both are equal then returns 0. It checks even based on the Case Values .

Syntax:

 object.compareToIgnoreCase(object2);

 11.contains(String): It is used to search the sequence of characters in a given String. If the sequence is present returns true otherwise false .

 Syntax:

 object.contains("Character to be searched");

 12.endsWith(String): It is used to check weather the sequence of character is ended in the given string or not . If the given character is equal to the end value of the String then this method returns true otherwise falls.

 Syntax:

 object.endsWith("character Sequence");

 13.indexOf("String or a character"): It is used to return the index of the given character or a String present in the String.

 Syntax:

 object.indexOf("character or a String");

 14.isEmpty(): It is used to return a boolean value . If the String is empty it returns true otherwise false.

 Syntax:

 object.isEmpty();

 15.replace(charSequence old , charequence new): It is used to replace the one character Sequence with other character Sequence.

 Syntax:

 object.replace(old characterSequence,new CharacterSequence);  
Program using String methods

import java.util.*;

 class StringMethods 
{
public static void main(String[] args) 
{
System.out.println("Enter A String value");

 Scanner sc=new Scanner(System.in);

 String str1=sc.next();

 System.out.println("Using Length Method:"+str1.length());

 System.out.println("Using CharAt Method:"+str1.charAt(2));

 System.out.println("Using toUpper Method:"+str1.toUpperCase());

 System.out.println("Using toLower Method:"+str1.toLowerCase());

 System.out.println("Using trim Method:"+str1.trim());

 System.out.println("Using isEmpty Method:"+str1.isEmpty());

 System.out.println("Using indexOf Method:"+str1.indexOf("M"));

 System.out.println("Using endsWith Method:"+str1.endsWith("n"));

System.out.println("Using replace Method:"+str1.replace("VoidMain","Void Main Technologies"));

 System.out.println("Using Contains Method:"+str1.contains("Void"));

 }

}

Save As:

StringMethods.java

Compile:

javac StringMethods.java

Run:

java StringMethods

Input:

Enter A String values

VoidMain

Output:

Using Length Method: 8

Using CharAt Method: i

 Using toUpper Method: VOIDMAIN

 Using toLower Method: voidmain

 Using trim Method: VoidMain

 Using isEmpty Method: false

 Using indexOf Method: 4

 Using endsWith Method: true

 Using replace Method: voidMainTechnologies

 Using Contains Method: true
Program using Some more String methods
import java.util.*;

 class StringMethods1 
{
public static void main(String[] args) 
{
System.out.println("Enter two String values");

 Scanner sc=new Scanner(System.in);

 String str1=sc.next();

 String str2=sc.next();

 System.out.println("Using equals Method:"+str1.equals(str2));

 System.out.println("Using concat Method:"+str1.concat(str2));

 System.out.println("Using compareTo Method:"+str1.compareTo(str2));

 System.out.println("Using compareToIgnoreCase Method:"+str1.compareToIgnoreCase(str2));

 }
}

Save As:

StringMethods.java

Compile:

javac StringMethods.java

Run:

java StringMethods

Input:

Enter two String values

Void
Main

Output:

 Using equals Method: false

Using concat Method: VoidMain

Using compareTo Method: 9 (Str1>Str2)

 Using compareToIgnoreCase Method: 9 (Str1>Str2).

StringBuffer Class: It is also same as String class but mutable (Objects of String Buffer Class can be modified or can be changed) . This can execute only one thread at a time , hence called as Synchronized class .

 Syntax:

 StringBuffer object=new StringBuffer();

 or 

 StringBuffer Object=new StringBuffer(String);

 or

 StringBuffer Object=new StringBuffer(int capacity);

Predefined Methods In StringBuffer Class 

1.append(String): it is used to combine two StringBuffers together. These method returns  String values . The overloaded methods for append are append(int) ,  append(char) , append(double) , append(float) , append(short int).

Syntax:

Object.append("String value");

2.insert(int,String): It is used to insert the String or a character at a specified position . These method returns a String value . It takes to parameters 
  1. Integer for specifying position to insert .
  2. String or character to be inserted .  
Syntax:

Object.insert(position,"String value");

3.reverse(): It is used for reversing the given String . It returns the String value . 

Syntax:

object.reverse();

4.capacity(): It is used to specify the capacity of a StringBuffer . It returns a integer value in bits format.

Syntax:

object.capacity();

5.ensureCapacity(int): It is used to create a StringBuffer atleast equal to specified value . The value changes as (old capacity*2)+2.

Syntax:

object.ensureCapacity(int value);

6.length(): It is used to return the length of the StringBuffer . It returns integer value .

Syntax:

Object.length();

7.replace(startIndex , endIndex , String): It is used to replace the String value specified between starting and ending index. It returns String value.

Syntax:

Object.replace(int,int,"String value");

8.delete(StartIndex , EndIndex): It is used to delete the String present between the Starting and Ending Index .

Syntax:

Object.delete(int,int);


Program using StringBuffer methods
import java.util.*;

class StringBufferMethods 
{
public static void main(String[] args) 
{
Scanner sc=new Scanner(System.in);

System.out.println("ENTER TWO STRING VALUES");

String s1=sc.next();

String s2=sc.next();
StringBuffer str1=new StringBuffer(s1);

StringBuffer str2=new StringBuffer(s2);
System.out.println("Using append Method:"+str1.append(str2));
System.out.println("Using insert Method:"+str1.insert(4,"M"));
System.out.println("Using reverse Method:"+str1.reverse());
System.out.println("Using capacity Method:"+str1.capacity());

System.out.println("Using length Method:"+str1.length());

System.out.println("Using replace Method:"+str1.replace(0,7,"VOIDMAIN"));
System.out.println("Using delete Method:"+str1.delete(0,3)); 
}
}

Save As:

StringBufferMethods.java

Compile:

javac StringBufferMethods.java


Run:

java StringBufferMethods

Input:

ENTER TWO STRING VALUES:

VoidMain
Technologies

Output:

Using append Method: voidMainTechnologies

Using insert Method:VoidMMainTechnologies

 Using reverse Method:seigolonhectniaMMdioV

 Using capacity Method:24

Using length Method: 21

 Using replace Method: VOIDMAINnhectniaMMdiov

 Using delete Method:DMAINnhectniaMMdiov.

 Note:

 Once String performs an operation then the original String is replaced with the String which is obtained as an output . Then the replaced String is used for the further operations.

 Example:

 From the above Program :

 str1=VoidMain , after performing the append operation str1  changed to str1=VoidMainTechnologies . Hence the changed str1 is used for the further operations .
3.StringBuilder Class: String Builder class is same as the String class but here multiple threads can execute at a time . These are also imputable objects . The Main difference between the String and String Builder class are Strings can execute only one thread at a time whereas String Buffer can execute multiple Threads at a time.

 Syntax:

 StringBuilder sb=new String Builder();

OR

StringBuilder sb=new StringBuilder(String);

 OR

 StringBuilder sb=new StringBuilder(capacity);

Predefined Methods In StringBuilder Class 

1.append(String): it is used to combine two StringBuffers together. These method returns  String values . The overloaded methods for append are append(int) ,  append(char) , append(double) , append(float) , append(short int).

Syntax:

Object.append("String value");

2.insert(int,String): It is used to insert the String or a character at a specified position . These method returns a String value . It takes to parameters 
  1. Integer for specifying position to insert .
  2. String or character to be inserted .  
Syntax:

Object.insert(position,"String value");

3.reverse(): It is used for reversing the given String . It returns the String value . 

Syntax:

object.reverse();

4.capacity(): It is used to specify the capacity of a StringBuffer . It returns a integer value in bits format.

Syntax:

object.capacity();

5.ensureCapacity(int): It is used to create a StringBuffer atleast equal to specified value . The value changes as (old capacity*2)+2.

Syntax:

object.ensureCapacity(int value);

6.length(): It is used to return the length of the StringBuffer . It returns integer value .

Syntax:

Object.length();

7.replace(startIndex , endIndex , String): It is used to replace the String value specified between starting and ending index. It returns String value.

Syntax:

Object.replace(int,int,"String value");

8.delete(StartIndex , EndIndex): It is used to delete the String present between the Starting and Ending Index .

Syntax:

Object.delete(int,int);

Program using StringBuilder methods
import java.util.*;

 class StringBuilderMethods 
{
public static void main(String[] args) 
{
Scanner sc=new Scanner(System.in);

 System.out.println("ENTER TWO STRING VALUES");

 String s1=sc.next();

 String s2=sc.next();

StringBuilder str1=new StringBuilder(s1);

 StringBuilder str2=new StringBuilder(s2);

System.out.println("Using append Method:"+str1.append(str2));

System.out.println("Using insert Method:"+str1.insert(4,"M"));

System.out.println("Using reverse Method:"+str1.reverse());

System.out.println("Using capacity Method:"+str1.capacity());

 System.out.println("Using length Method:"+str1.length());

 System.out.println("Using replace Method:"+str1.replace(0,7,"VOIDMAIN"));

System.out.println("Using delete Method:"+str1.delete(0,3));
}

}

Save As:

StringBufferMethods.java

Compile:

javac StringBuilderMethods.java


Run:

java StringBuilderMethods

Input:

ENTER TWO STRING VALUES:

VoidMain
Technologies

Output:

Using append Method: voidMainTechnologies

Using insert Method:VoidMMainTechnologies

Using reverse Method:seigolonhectniaMMdioV

Using capacity Method:24

Using length Method: 21

Using replace Method: VOIDMAINnhectniaMMdiov

Using delete Method:DMAINnhectniaMMdiov.

Note:

 String Builder class supports both the methods of String Buffer and String class.

 4.StringTokenizer class: String Tockenizer is used to divide the String into tokens .

 Syntax:

 StringTokenizer st=new StringTokenizer(Srting);

 OR

 StringTokenizer st=new StringTokenizer(String , deli-meter);

 OR

 StringTokenizer st=new StringTokenizer(String , deli-meter, flag);

Predefined Methods In StringTokenizer Class

1.nextToken(): These method returns the next Token in the given String .

Syntax:

Object.nextToken();

2.nextToken(deli-meter): These method is used to return the Token based on the deli-meter.

Syntax:

Object.nextToken(deli-meter);

3.hasMoreToken(); These method is used to return the boolean value . If more tokens are present returns true otherwise false.

Syntax:

Object.hasMoreTokens();

4.hasMoreElements(); These method returns a boolean value . If it has more elements returns true otherwise false.

Syntax:

Object.hasMoreElements();

5.nextElement(): These method is used to return a boolean value . If the element is present returns true otherwise false.

Syntax:

Object.nextElement();

Program using StringTokenizer methods


import java.util.*;


class StringTokenizerMethods 
{
public static void main(String[] args) 
{
System.out.println("String Tokenizer Methods");

Scanner sc=new Scanner(System.in);

System.out.println("ENTER STRING VALUE");

String s1=sc.next();

StringTokenizer str1=new StringTokenizer(s1,",");
System.out.println("Using nextToken Method:"+str1.nextToken());
System.out.println("Using nextTocken with deli-meter:"+str1.nextToken(","));
System.out.println("Using hasMoreTockens Method:"+str1.hasMoreTokens());
System.out.println("Using hasMoreElements Method:"+str1.hasMoreElements());

}
}

Save As:

StringTokenizerMethods.java

Compile:

javac StringTokenizerMethods.java


Run:

java StringTokenizerMethods

Input:

String Tokenizer Methods

ENTER STRING VALUE:

VoidMain,Technologies

Output:

Using nextToke method: voidMain


Using nextTocken with deli-meter:Technologies


Using hasMoreTockens Method:false

hasMoreElements Method:false

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