StringBuffer
CLASS
So let’s see the syntax of the how to declare a StringBuffer
constructor in Java:
StringBuffer str = new
StringBuffer(int Size);
Now note that if the capacity of the string is not mentioned
inside the parentheses (Ex: StringBuffer str = new
StringBuffer(); ) the compiler by default we allocate the capacity for 16
characters to that the string, but obviously that’d be extendable. Now let’s
have a look at another way in which we can initialise the String with the
constructor.
StringBuffer str = new
StringBuffer(“Hello Readers”);
Note that when the String value is declared right away with
the constructor the capacity of the string increases to 16 + (the current length
of the string).
Now let us understand the methods that we have for the
StringBuffer class.
i) length()
& capacity() : So by the name you might have guessed it right that
what does these methods do. ‘.length()’ tells us the current length of the
String and (.capacity()) tell us the capacity of the String.
Ex:
public class StringBuffer_class {
public static void main(String[] args) {
StringBuffer
STR = new
StringBuffer();
StringBuffer
STR2 = new
StringBuffer("Coding
Winds");
System.out.println(STR);
System.out.println("length of STR :"+STR.length()+"\ncapacity of STR:"+STR.capacity());
System.out.println("\n"+STR2);
System.out.println("length of STR2 :"+STR2.length()+"\ncapacity of STR2:"+STR2.capacity());
}
}
OUTPUT:
length of STR :0
capacity of STR:16
Coding Winds
length of STR2 :12
capacity of STR2:28
So one can see above, that when the String has no value (or
when its length is 0) and is declared without the size, then the capacity of
the string (pre allocated ) is 16, but when it has some value the capacity is
increased to 16+(length of the string) , i.e., 28 for the above case.
ii)append()
: This method can be used to add (or append) something at the end of a
String.
Ex:
public class StringBuffer_class {
public static void main(String[] args) {
StringBuffer
STR = new
StringBuffer("Coding");
STR.append("
Winds");
System.out.println(STR);
}
}
OUTPUT:
Coding Winds
iii)insert() : This method is used to insert a string or number at an specific index
( .insert(int index, “String”); )
Ex:
public class StringBuffer_class {
public static void main(String[] args) {
StringBuffer
STR = new
StringBuffer("Hello");
STR.append("
People!");
STR.insert(13," What's up?");
STR.insert(24, 10); /*integers can be written without double quotes */
System.out.println(STR);
}
}
OUTPUT:
Hello People! What's up?10
iv)reverse() : As the method name suggests itself, it is used to reverse a String
Ex:
public class StringBuffer_class {
public static void main(String[] args) {
StringBuffer
STR = new
StringBuffer("YENSID");
STR.reverse();
System.out.println(STR);
}
}
OUTPUT:
DISNEY
v) .delete() & .deleteCharAt() : These two methods
are used to delete the characters of a string of some indexes and at a
particular index , respectively.
Ex:
public class StringBuffer_class {
public static void main(String[] args) {
StringBuffer
STR = new
StringBuffer("YENSID");
STR.delete(0,3);
System.out.println(STR);
StringBuffer
STR2 = new
StringBuffer("Hello 2
All");
STR2.deleteCharAt(6);
System.out.println(STR2);
}
}
OUTPUT:
SID
Hello
All
vi) .replace(): This method is used to replace a certain part of the string with a new
one.
Syntax:
stringName.replace(int startIndex, int
endIndex, “new string”);
Ex:
public class StringBuffer_class {
public static void main(String[] args) {
StringBuffer
STR = new
StringBuffer("Hello 2
All");
STR.replace(6,7,"to");
System.out.println(STR);
}
}
OUTPUT:
Hello to All
vii)
setCharAt(): This method sets a new char at the specified index:
public class StringBuffer_class {
public static void main(String[] args) {
StringBuffer
STR = new
StringBuffer("Hello All");
STR.setCharAt(6, '2');
System.out.println(STR);
}
}
OUTPUT:
Hello 2 All
viii) setLength(): Modifies the length of the string to the specified length:
Ex:
public class HackerRank {
public static void main(String[] args) {
StringBuffer
STR = new
StringBuffer("Hello 2
All");
STR.setLength(20);
STR.setCharAt(19, 'x');
System.out.println(STR);
System.out.println(STR.length());
}
}
OUTPUT:
Hello 2 All x
20
ix) trimToSize() : This method is used to trim the capacity of the string to its size:
Ex:
public class StringBuffer_class {
public static void main(String[] args) {
StringBuffer
STR = new
StringBuffer("Hello
People");
System.out.println(STR.capacity());
STR.trimToSize();
System.out.println(STR.capacity());
}
}
OUTPUT:
28
12
