StringBuilder

Java StringBuilder class

Java StringBuilder class is used to create mutable (modifiable) string. The Java StringBuilder class is same as StringBuffer class except that it is non-synchronized. It is available since JDK 1.5.

Let's see the examples of different methods of StringBuilder class.

1) StringBuilder append() method

The StringBuilder append() method concatenates the given argument with this string.

1. class StringBuilderExample{  
2. public static void main(String args[]){  
3. StringBuilder sb=new StringBuilder("Hello ");  
4. sb.append("Java");//now original string is changed  
5. System.out.println(sb);//prints Hello Java  
6. }  
7. } 

2) StringBuilder insert() method

The StringBuilder insert() method inserts the given string with this string at the given position.

1. class StringBuilderExample2{  
2. public static void main(String args[]){  
3. StringBuilder sb=new StringBuilder("Hello ");  
4. sb.insert(1,"Java");//now original string is changed  
5. System.out.println(sb);//prints HJavaello  
6. }  
7. }  

3) StringBuilder replace() method

The StringBuilder replace() method replaces the given string from the specified beginIndex and endIndex.

1. class StringBuilderExample3{  
2. public static void main(String args[]){  
3. StringBuilder sb=new StringBuilder("Hello");  
4. sb.replace(1,3,"Java");  
5. System.out.println(sb);//prints HJavalo  
6. }  
7. }  

4) StringBuilder delete() method

The delete() method of StringBuilder class deletes the string from the specified beginIndex to endIndex.

1. class StringBuilderExample4{  
2. public static void main(String args[]){  
3. StringBuilder sb=new StringBuilder("Hello");  
4. sb.delete(1,3);  
5. System.out.println(sb);//prints Hlo  
6. }  
7. }  

5) StringBuilder reverse() method

The reverse() method of StringBuilder class reverses the current string.

1. class StringBuilderExample5{  
2. public static void main(String args[]){  
3. StringBuilder sb=new StringBuilder("Hello");  
4. sb.reverse();  
5. System.out.println(sb);//prints olleH  
6. }  
7. }  

6) StringBuilder capacity() method

The capacity() method of StringBuilder class returns the current capacity of the Builder. The default capacity of the Builder is 16. If the number of character increases from its current capacity, it increases the capacity by (oldcapacity*2)+2. For example if your current capacity is 16, it will be (16*2)+2=34.

1. class StringBuilderExample6{  
2. public static void main(String args[]){  
3. StringBuilder sb=new StringBuilder();  
4. System.out.println(sb.capacity());//default 16  
5. sb.append("Hello");  
6. System.out.println(sb.capacity());//now 16  
7. sb.append("java is my favourite language");  
8. System.out.println(sb.capacity());//now (16*2)+2=34 i.e (oldcapacity*2)+2  
9. }  
10. }