String Buffer and String Builder

The StringBuffer and StringBuilder classes are used when there is a necessity to make a lot of modifications to Strings of characters.

StringBuffer class is used to create a mutable string object. It represents growable and writable character sequence. As we know that String objects are immutable, 

Note: so if we do a lot of changes with String objects, we will end up with a lot of memory leak.

So StringBuffer class is used when we have to make lot of modifications to our string. 

Note: Term Thread Safety--> It means to stay safe from Thread because of many threads come it will become unsafe.

Append in String Buffer

package mypackage;

import java.util.Random;

public class test{

      

       public static void main(String[] args) {

       StringBuffer sb=new StringBuffer();

       sb.append("test");

       sb.append("hello");

       System.out.println(sb);

       }

}

Output:

testhello

StringBuffer with parameter

package mypackage;

import java.util.Random;

public class test{

       public static void main(String[] args) {

             StringBuffer sb=new StringBuffer("test");//pass value in parameter

             sb.append("hello");

             System.out.println(sb);

       }

}

String Buffer insert function

package mypackage;

public class test{

       public static void main(String[] args) {

      

             StringBuffer sb=new StringBuffer("test");

             sb.insert(3, "hello");//3 is the position on which you want to insert

             System.out.println(sb);

       }

}

Output:

teshellot

Delete character from String Buffer

package mypackage;

public class test{

       public static void main(String[] args) {

      

             StringBuffer sb=new StringBuffer("test  ");

             sb.deleteCharAt(1);

             System.out.println(sb);

       }

}

Output:

tst 

Index of String

package mypackage;

public class test{

       public static void main(String[] args) {

      

             StringBuffer sb=new StringBuffer("test  ");

             int number=sb.indexOf("e");

             System.out.println(number);

       }

}

Output:

1

To replace in String Buffer

package mypackage;

public class test{

       public static void main(String[] args) {

      

             StringBuffer sb=new StringBuffer("test  ");

             sb.replace(1, 2, "hello");

             System.out.println(sb);

       }

}

Output:

thellost 

String concat does not update the string

package mypackage;

public class test{

       public static void main(String[] args) {

            

             String name="neeraj";

             name.concat("hello");//it will not make name=neerajhello

             System.out.println(name+"test");//we will have to concat in this way using + operator

             String hello=name+"test";

             System.out.println(hello);

            

       }

}

Output:

neerajtest

neerajtest

String Builder

Difference between StringBuffer and StringBuilder

StringBuffer      StringBuilder

1) StringBuffer is synchronized i.e. thread safe. It means two threads can't call the methods of StringBuffer simultaneously.     

StringBuilder is non-synchronized i.e. not thread safe. It means two threads can call the methods of StringBuilder simultaneously.

2) StringBuffer is less efficient than StringBuilder.

StringBuilder is more efficient than StringBuffer.

By thread safe in the general terms means that even if you run multiple threads simultaneously on the same resources even in such a condition those threads won’t get stuck in a deadlock. It is the state in which sometimes all the threads can come to a stand still because of an endless loop of not getting the required resource.

The basic fix which java uses is the keyword “synchronized” only methods or block of codes can be marked as synchronized. This makes sure that only a single thread is working on a particular object helping in avoiding the situation of a deadlock.

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                                    String                    StringBuffer         StringBuilder
----------------------------------------------------------------------------------                 
Storage Area | Constant String Pool           Heap                       Heap 
Modifiable     |  No (immutable)            Yes( mutable )          Yes( mutable )
Thread Safe   |           Yes                                  Yes                              No
 Performance |         Fast                                Very slow                    Fast
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