Compare Values using Relational Operators in JAVA

In the term relational operator, relational refers to the relationships that values (or operands) can have with one another. Thus, the relational operators determine the relation among different operands.

Java provides six relational operator for comparing numbers and characters. But they don’t work with strings. If the comparison is true, the relational expression results into the Boolean value true and to Boolean value false, if the comparison is false. The six relational operators are:

• < (less than)
• <= (less than or equal to)
• == (equal to)
• > (greater than)
• >= (greater than or equal to) and
• != (not equal to)

Summarizes the action of these relational operators.

t represents true and f represents false.
The relational operators have a lower precedence than the arithmetic operators. That means the expression
a + 5 > c – 2  ...expression 1
Corresponds to
( a + 5 ) > ( c – 2 ) ...expression 2
And not the following
a + ( 5 > c ) -2  …expression 3

Though relational operators are easy to work with, yet while working with them, sometimes you get unexpected results and behavior from your program. To avoid so, we would like you to know certain tips regarding relational operators.

Do not confuse the = and the = = operators.

A very common mistake is to use the assignment operators (=) in place of the relational operator (==). Do not confuse the testing the operator (==) with the assignment operator (=). For instance, the expression
Value = 3
Tests whether value is equal to 3? The expression has the Boolean value true if the comparison is true and Boolean false if it is false.

But the expression
Value = 3
Assigns 3 to value. The whole expression, in the case, has the value 3 because that’s the value of the left-hand side.

Avoid equality comparisons on floating-point numbers.

Floating-point arithmetic is not as exact and accurate as the integer arithmetic is. For instance, 3 X 5 is exactly 15, but 3.25 X 5.25 is nearly equal to 17.06 (if we are working with number with 2 decimal places). The exact number resulting from 3.25 X 5.25 is 17.0625.

Therefore, after any calculation involving floating-point numbers, there may be a small residue error. Because of this error, you should avoid the equality and inequality comparisons on floating-point number.

The relational operators group Left-to-right i. e., a <b<c means (a <b) < c and not a < ( b < c ).

Postfix version of operators 

How to use LINQ Conversion operators in ASP.NET

Introduction

Conversion operators convert a collection to an array. A Conversion operator changes the type of input objects. The different Conversion operators are ToSequence, ToArray, ToList, ToDictionary, ToLookup, OfType, and Cast.
The ToSequence clause simply returns the source argument by changing it to IEnumerable<T>. The ToArray clause enumerates the source sequence and returns an array containing the elements of the sequence. The ToList clause enumerates the source sequence and returns a List<T> containing the elements of the sequence. The ToDictionary clause lists the source sequence and evaluates the keySelector and elementSelector functions for each element to produce the element key and value of the source sequence. The ToLookup clause implements one-to-many dictionary that maps the key to the sequence of values. The OfType clause allocates and returns an enumerable object that captures the source argument. The Cast clause also allocates and returns an enumerable object that captures the source argument.
The syntax of the ToList clause is:


For C#
public static List<T> ToList<T>( this IEnumerable<T> source);

Lets take an simple example

<form id="form1" runat="server">
    <div>
 
        <asp:ListBox ID="ListBox1" runat="server" Height="143px" Width="143px">
        </asp:ListBox>
        <br />
        <asp:Button ID="Button1" runat="server" onclick="Button1_Click"
            Text="String type" />
        <asp:Button ID="Button2" runat="server" onclick="Button2_Click"
            Text="Integer Type" />
 
    </div>
    </form>
Code Behind
protected void Button1_Click(object sender, EventArgs e)
    {
        ListBox1.Items.Clear();
        var strtype = list.OfType<string>();
        ListBox1.Items.Add("String type value");
        foreach (var item in strtype)
        {
            ListBox1.Items.Add(item);
        }
    }
    protected void Button2_Click(object sender, EventArgs e)
    {

        ListBox1.Items.Clear();
        var strtype = list.OfType<int>();
        ListBox1.Items.Add("integer type value");
        foreach (var item in strtype)
        {
            ListBox1.Items.Add(item.ToString ());
        }

    }
Code Generate the following output

How to use LINQ Set Operators in ASP.NET

Introduction

The Set operators in LINQ refer to the query operations that produce a result set. The result is based on the presence or absence of the equivalent elements that are present within the same or separate collection. The Distinct, Union, Intersect, and Except clauses are classified as the Set operators. The Distinct clause removes duplicate values from a collection.
The syntax of the Distinct clause is:
For C#
public static IEnumerable<T> Distinct<T>( this IEnumerabIe<T> source);

The Union clause returns the union of two sets. The result elements are the unique elements that are common in the two sets.
The syntax of the Union clause is:
For C#
public static IEnumerabIe<T> Union<T>( this IEnumerabIe<T> source1, IEnumerabIe<T> source2);

The Intersect clause returns the set intersection. The elements appear in each of the two collections.
The syntax of the Intersect clause is:
For C#
public static IEnumerabIe<T> Intersect<T>( this IEnumerabIe<T> source1, IEnumerabIe<T> source2);
The Except clause returns the set difference. The result of the Except clause returns the elements of one collection that do not appear in the second collection.
The syntax of the Except clause is:
For C#
public static 1Enumerable<T> Except<T>( this 1Enumerable<T> sourcel, IEnumerab1e<T> source2);

lets take an simple example

Source Code
<form id="form1" runat="server">
    <div>
    
    </div>
    <asp:ListBox ID="ListBox1" runat="server" Height="137px" Width="221px">
    </asp:ListBox>
    <br />
    <asp:Button ID="Button1" runat="server" onclick="Button1_Click" 
        Text="common word" />
    </form>
Code behind
protected void Button1_Click(object sender, EventArgs e)
    {
        string[] fruits = { "apple", "mango", "banana" };
        string[] wds = { "my world", "mango", "operation" };
        var common = fruits.Intersect(wds);
        ListBox1.Items.Add("common in both array");
        foreach (var item in common)
        {
            ListBox1.Items.Add(item);
        }
    }
Code Generate the following output

How to add hour, minute and seconds in existing time ASP.NET Example

Introduction

If you want to add hour, minute and seconds in existing time then you should take TimeSpan structure with overload function. Now, you can easily add TimeSpan structure with existing date time object using Add method. Lets take an simple example for demonstration.
Step-1 : Add new web form into the project
Step-2 : Add one button and label control on it.
Step-3 : Handle Button click event.

<form id="form1"
    runat="server">
    <asp:Button ID="Button1"
    runat="server"
    BackColor="#33CCFF"
    onclick="Button1_Click"
    Text="Click" />
    <div>  
    <asp:Label ID="Label1"
    runat="server"
    BackColor="Yellow"></asp:Label>  
    </div>
    </form>
Code Behind
 protected void Button1_Click(object sender, EventArgs e)
        {          
            DateTime now = DateTime.Now;    
            TimeSpan TR = new TimeSpan(3, 41, 11);
            DateTime afterAddedSpanTime = now.Add(TR);
            Label1.Text = "current time : " + now.ToLongTimeString();
            Label1.Text += "<br /><br />";
            Label1.Text += "after added a spantime with current time <br />";
            Label1.Text += "time span: 3 hours|41 minutes|11 seconds <br />";
            Label1.Text += afterAddedSpanTime.ToLongTimeString();

        }
Code Generate the following output

How to show AM and PM with time in ASP.NET

Introduction

You can show System time as well as universal time through DateTime class. Now, this time you want to show only am and pm text after the current time. You can use "tt" in the ToString ( ) method. Lets create an simple algorithm.
Step-1 : Take a web form into the project
Step-2 : Add two control (button and label control) onto the form window.
Step-3 : Raise button click event
Step-4 : Take single instance of DateTime class also pass "tt" parameter in ToString ( ) method.
Step-5 : Now Run your application from green triangle button or Ctrl+f5

Complete Source Code

<form id="form1" runat="server">
    <div>
   
        <asp:Button ID="Button1"
         runat="server"
         onclick="Button1_Click"
         Text="Click"
         BackColor="#99CCFF" />  
    </div>
        <asp:Label ID="Label1"
        runat="server"
        Text="Label"
        BackColor="Yellow"></asp:Label>
    </form>
Code Behind
 protected void Button1_Click(object sender, EventArgs e)
        {
          DateTime now = DateTime.Now;          
            Label1.Text = "current time PM AM: " + now.ToLongTimeString();
            Label1.Text += "<br /><br />";          
            Label1.Text += "current time [PM AM]: " + now.ToString("tt");

        }
Code generate the following output

How to find first day of next month in ASP.NET

If you want to get first day of next month , use DateTime structure with AddMonths( ) method. using this method you can get first day of next month. Now, create a new instance of DateTime structure with some parameter like DateTime(Int32, Int32, Int32). This parameterized method Initializes a new instance of the DateTime structure to the specified year, month, and day. Here you can pass integer 2 in day field. Now, you can delete 1 day from current DateTime object using AddDays (-1) method.

Source Code 

 <form id="form1" runat="server">
    <div>  
        <asp:Button ID="Button1"
        runat="server"
        BackColor="#66CCFF"
        onclick="Button1_Click"
        Text="Click" />  
    </div>
       <asp:Label ID="Label1"
       runat="server"
       BackColor="Yellow"
       Text="Label"></asp:Label>
    </form>

Code Behind

 protected void Button1_Click(object sender, EventArgs e)
        {            
            DateTime today = DateTime.Today;            
            DateTime tempDate = today.AddMonths(1);
            DateTime tempDate2 = new DateTime(tempDate.Year, tempDate.Month, 2);
            DateTime nextmonthfirstday = tempDate2.AddDays(-1);
            Label1.Text = "Today : " + today.ToLongDateString();
            Label1.Text += "<br /><br />next month first day = ";
            Label1.Text += nextmonthfirstday.ToLongDateString();

        }

Code Generate the following output

How to Create DropDownList in Asp.Net MVC

Drop down list is a common and usable control in every programming area to let the user can select only one item from the list. In MVC we have to create a list in action method of controller and then pass it through any method like ViewBag and ViewModel etc.

Programmer can create required type of list as per the requirements, we will create a SelectListItem type of list because this list provides two property Text and Value by default. Create a simple list of type SelectListItem and add some items (we have added four item here) as added below:

List<SelectListItem> items = new List<SelectListItem>();
items.Add(new SelectListItem { Text = "Value 1", Value = "1" });
items.Add(new SelectListItem { Text = "Value 2", Value = "2" });
items.Add(new SelectListItem { Text = "Value 3", Value = "3" });
items.Add(new SelectListItem { Text = "Other", Value = "4" });

Now to pass this to View page write a single line as written below:

ViewBag.ddlItems = new SelectList(items, "Value", "Text");

Value will be the dataValue field and Text will be dataText field for this dropdownlist. In the view page create a form and of course a dropdownlist with a submit button:

@using (Html.BeginForm())
{
    <div>
        @Html.DropDownList("selectedItem", (IEnumerable<SelectListItem>)ViewBag.ddlItems)
        <input type="submit" value="Submit" id="submitBtn" />
    </div>
}

First parameters of this helper Html.DropDownList() specifies name of the HTML select element, and also the name of the view model property that is bound to the element. Second parameter shows the list of options of select list.

This will create a dropdownlist with a submit button. Run the application and open particular view in the browser. Select any value and then submit. Oops! i haven't write the code to access the selected value. So write HttpPost type of action:

public ActionResult Index(string selectedItem)
{
....
....

Here parameter selectedItem is the same name of dropdownlist we have assigned in the view page. Again run the application, select any value("Value 2") and then submit. This parameter will contain the selected value(2).

CheckboxList in MVC