Stack is a subclass of Vector that implements a standard last-in, first-out stack. Stack only defines the default constructor, which creates an empty stack. Stack includes all the methods defined by Vector, and adds several of its own. Stack( ) Apart from the methods inherited from its parent class Vector, Stack defines the following methods − Sr.No. Method & Description 1 boolean empty() Tests if this stack is empty. Returns true if the stack is empty, and returns false if the stack contains elements. 2 Object peek( ) Returns the element ... Read More

As we know that Hash map in Java does not maintain insertion order either by key or by order.Also it does not maintain any other order while adding entries to it. Now in order to sort a hash map according to the values mapped to its corresponding keys we first need to get all values of map considering that hash map has unique values only.Now put all the values in a list and sort this list with the comparator or comparable interface of Java. As we get sorted list of unique values now get corresponding keys from the map and ... Read More

The FILTER_VALIDATE_URL constant validates a URL.FlagsFILTER_FLAG_SCHEME_REQUIRED − URL must be RFC compliant.FILTER_FLAG_HOST_REQUIRED − URL must include host name.FILTER_FLAG_PATH_REQUIRED −URL must have a path after the domain name.FILTER_FLAG_QUERY_REQUIRED −URL must have a query string.ReturnThe FILTER_VALIDATE_URL constant does not return anything.Example Live DemoOutputThe following is the output.Valid URL!Let us see another example.Example Live DemoOutputHere is the output.Invalid URL!

The FILTER_VALIDATE_REGEXP constant validates a value against a Perl-compatible regular expression. Options regexp − The regular expression to validate against. Return The FILTER_VALIDATE_REGEXP constant does not return anything. Example Live Demo The following is the output. Matched String!

The FILTER_VALIDATE_IP constant validates an IP address. Flags FILTER_FLAG_IPV4 − The value must be a valid IPv4 address FILTER_FLAG_IPV6 − The value must be a valid IPv6 address FILTER_FLAG_NO_PRIV_RANGE − The value must not be within a private range FILTER_FLAG_NO_RES_RANGE − The value must not be within a reserved range Return The FILTER_VALIDATE_IP constant does not return anything. Example Live Demo The following is the output. Invalid IP address! Let us see another example. Live Demo Here is the output. Valid IP address!

In order to sort in Java as we know we can use either Comparable or Comparator interfaces in which we could also define our custom logic to sort.One of the approach to sort is to add the entity in TreeSet or TreeMap which would sort the entries as internally they also uses the comparable interface. Now String class in Java internally implements comparable interface so whenever we add string to a tree set or map it uses comparable logic of string class and sort the input entry strings.But String buffer do not have the implementation of comparable interface so ... Read More

The FILTER_VALIDATE_INT constant validates value as integer.Options and flagsmin_range − The minimum integer valuemax_range − The maximum integer valueFILTER_FLAG_ALLOW_OCTAL − Allows octal number valuesFILTER_FLAG_ALLOW_HEX − Allows hexadecimal number valuesReturnThe FILTER_VALIDATE_INT constant does not return anything.Example Live DemoOutputThe following is the output.float(3.5) Integer VariableLet us see another example.Example Live DemoOutputHere is the output.Accepted range!

The FILTER_VALIDATE_FLOAT constant validates a value as a float number.ReturnThe FILTER_VALIDATE_FLOAT constant does not return anything.Example Live DemoOutputThe following is the output.float(291.9)

The FILTER_VALIDATE_EMAIL() constant validates an email address.ReturnThe FILTER_VALIDATE_EMAIL() does not return anything.Example Live DemoOutputThe following is the output.examplee@demo.com = valid email address

The FILTER_VALIDATE_BOOLEAN constant validates value as a boolean option.ReturnThe FILTER_VALIDATE_BOOLEAN constant returns TRUE for "1", "true", "on" and "yes". It returns FALSE for "0", "false", "off" and "no" otherwise, NULL.Example Live DemoOutputThe following is the output.bool(true)ExampleLet us see another example.OutputHere is the output.bool(false)