3.7_StringBuilder.pdf

String Builder 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.
Constructor Description
StringBuilder() It creates an empty String Builder with the initial capacity of
16.
StringBuilder(String str) It creates a String Builder with the specified string.
StringBuilder(int length) It creates an empty String Builder with the specified
capacity as length.

Method Description
public StringBuilder append(String s) It is used to append the specified string with this string. The
append() method is overloaded like append(char),
append(boolean), append(int), append(float), append(double)
etc.
public StringBuilder insert(int offset, String s) It is used to insert the specified string with this string at the
specified position. The insert() method is overloaded like
insert(int, char), insert(int, boolean), insert(int, int),
insert(int, float), insert(int, double) etc.
public StringBuilder replace(int startIndex, int
endIndex, String str)
It is used to replace the string from specified startIndex and
endIndex.
public StringBuilder delete(int startIndex, int
endIndex)
It is used to delete the string from specified startIndex and
endIndex.
public StringBuilder reverse() It is used to reverse the string.

public int capacity() It is used to return the current capacity.
public void ensureCapacity(int
minimumCapacity)
It is used to ensure the capacity at least equal to the
given minimum.
public char charAt(int index) It is used to return the character at the specified
position.
public int length() It is used to return the length of the string i.e. total
number of characters.
public String substring(int beginIndex) It is used to return the substring from the specified
beginIndex.
public String substring(int beginIndex, int
endIndex)
It is used to return the substring from the specified
beginIndex and endIndex.

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

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

No. String StringBuffer
1) The String class is immutable. The StringBuffer class is mutable.
2) String is slow and consumes more memory when
we concatenate too many strings because every
time it creates new instance.
StringBuffer is fast and consumes less memory when
we concatenate t strings.
3) String class overrides the equals() method of
Object class. So you can compare the contents of
two strings by equals() method.
StringBuffer class doesn't override the equals()
method of Object class.
4) String class is slower while performing
concatenation operation.
StringBuffer class is faster while performing
concatenation operation.
5) String class uses String constant pool. StringBuffer uses Heap memory

No 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.
3) StringBuffer was introduced in Java 1.0 StringBuilder was introduced in Java 1.5

3.7_StringBuilder.pdf

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