Example for Customized Immutable Class

public final class MyString
{

private final char[] value;

private int length;

public MyString()
{

length=0;
value=new char[length];
}

public MyString(char c[])
{

length=c.length;
value=new char[length];
System.arraycopy(c, 0, value, 0, length);
}

public String toString()
{

return new String(value);
}

public MyString concat(MyString s)
{

char temp[]=new char[length+s.length()];
System.arraycopy(value, 0, temp, 0, length);
System.arraycopy(s.value, 0, temp, length, s.length());
MyString str=new MyString(temp);
return str;
}

public int length()
{

return length;
}
}