Control Statements in Java: What Do You Need to Know in 2020

What is Control Statement?

Control Statements interpolates the concept of modifying the flow of your code. When it comes to coding, you have to understand that the computer runs through your code in a specific way and executes most of the code from top to bottom. It goes to the first line, then to the second line, and so on till it reaches the bottom of the code from left to right.

This means that it fetches the value on the right-hand side and assigns into the left-hand side of the variable, as a general rule, but every rule has an exception which introduces the Control Structures or statements.

If you want to modify the sequential execution of the code flow, you have to do a transfer of control or use the control structure. A control statement determines whether the next set of tasks have to be executed or not.

Let us explain the control structure with a simple example using an “if” statement, a type of decision-making control statement. Java is a case sensitive language, which implies that the case structure has to be specific. IF cannot be capitalized, let us write something inside the if statement to determine whether or not a particular thing is true or false.

In this case, declare a variable called “name,” assign a value to that “name,” and check the value of the name. If the value is not equal to null, then action must be performed, like a print out the title to the Java console or output the value inside the variable called “name.” This helps to know what is going on in the application in real-time.

We evaluate an expression inside a control structure and determine whether the condition is true or false. If the expression evaluates to the wrong inside a control structure, it skips everything inside the scope of that particular control structure, skips the line of code, and goes outside and ends the program.

Read: Java Interview Questions & Answers

Control Structures or Statements in Java

The following are the Control structures that can be applied to any computer program. Control Statements are the essential structuring elements for the flow of program execution. They can branch, break, or advance program execution flow based on the change in program states.

Sequence Structure

This structure refers to the sequential execution of statements one after the other, as specified in the code. This is the default structure built into Java wherein the statements are executed one after the other from beginning to end unless instructed otherwise.

Selection Structure

This structure will let us choose a path based on a given condition. Java has three types of Selection statements, namely, if statement, if-else-statement, and switch statement. Selection statements are also called as decision-making statements. If and switch statements allow you to control the program execution flow based on the condition at runtime.

If Statement

This statement allows the program to start, reach a decision based on the set condition. This means a code can or cannot be executed.

Example:

If (x<20) {

System.out.printIn(“Hello Universe!”);

}

If-else-else Statement

The program starts and reads the decision based on the set condition and continues to do one thing or another and concludes.

Example:

If (x<20) {

System.out.printIn(“Hello Universe!”);

}

Else {

System.out.printIn(“Hello folks!”);

}

Switch or break Statement

The program starts, reach decisions to be made. A variable is compared to different values, and depending on the variable cost, a certain path of execution is chosen. Hence, other choices are available for the program to conclude.

Example:

switch (dayNumber) {

Case 1:

dayName = “Monday”;

break;

Case 2:

dayName = “Tuesday”;

break;

Case 3:

dayName = “Wednesday”;

break;

default:

dayName = “Any other Day”;

break;

}

Must Read: Pattern Programs in Java

Repetition Structure

Repetition structure allows us to execute code statements repetitively or zero times, depending on the condition.

We have three types of repetition/ looping statements/iteration in Java, namely, for a statement, while information, and do while statement. Iteration statements enable program execution to repeat one or more statements, such as a loop, for a loop. Each loop has four types of statements, namely,

  • Initialization
  • Condition Checking
  • Execution
  • Increment/Decrement

For Loop

This statement is used when the number of iterations is known before entering the loop. This loop is used to evaluate the initial value statements to the final value with a given increment/decrement.

Example:

for(m=1;m<=20;m=m+1)

{

  System.out.println(m);

}

classfor1

{

  public static void main(String args[])

{

int i;

for (i=0;i<5;i++)

{ 

      System.out.println(“\nExample of for loop”);

  }

}

Output:

Example of for loop

Example of for loop

Example of for loop

Example of for loop

Example of for loop

 

Example:

for(int i=20; i>1; i–) {

System.out.printIn(“The value of i is: ” + i);

}

The control variable is initialized and repeated as long as the condition is true, and when the condition is false, the program ends.

While Loop

This loop is used to evaluate the statements from the initial value to the final value with a given increment/decrement.

loop.

m=1

while(m<=20)

{

 System.out.printIn(m);

 m=m+1;

}

Example

print values from 1 to 10

Class while1

{

  public static void main(String aargs[])

  {

inti=1;

while(i<=10)

{

      System.out.printIn(“\n” + i);

   i++;

}

  }

}

Output:

1

2

3

4

5

6

7

8

9

10

do while loop

This loop is used to evaluate the statements from initial value to final value with given increment/decrement

m=1

do

{

System.out.printIn(m);

m=m+1;

}

while(m==20);

 

class dowhile1

{

  public static void main(String args[])

  {

int i = 1;

int sum = 0;

do

{

    sum = sum + i;

    i++;

}while (i<=10);

    System.out.printIn(‘\n\n\iThe sum of1to 10 is..” + sum);

  }

}

Output:

The sum of 1 to 10 is ..55

One of the major differences between the while loop and the do-while loop is that in a do-while loop, you will be executing the body of the loop initially and then check the condition. the do-while loop executes the block of the statement even when the condition fails, and it executes one time.

Branching Statements

Break, continue, and Return fall under the Branching Statements.

When we are working with looping statement, it is sometimes desirable to escape some statements inside the loop or terminate the loop immediately without checking the test expression. In that case, break and continue statements are used. These are the keywords that should be returned, followed by a semicolon. The break statement causes an immediate exit from loops or switch blocks for the execution of break statements. The control moves to this statement just after the loop objects which block or body of the loop. The break statement will break the loop and terminate it from the loop. The continue statement escapes the rest of the current iteration and proceeds with the loop’s next iteration. In the case of do-while, the control of the program moves to the test expression for further iteration. In the case of a loop, the control moves to the update expression.

Break Statement

Break statement has two forms, namely labeled and unlabeled. Break-in unlabeled switch statements can also be used to terminate the while do-while loop. Let us explain with an example.

Java switch statement is like an if-else statement that executes one of the conditions based on the switch input. In general, after the case is evaluated, even after the first match is met unless break is used inside the case to exit, the switch new possible values are listed using the case labels. These labels in Java may contain only constants. Execution will start after the layer. An optional default label may also be present to declare that the code will be executed. 

We are sending an argument, passing it to an integer, namely marks, and the marks variable goes to switch as a parameter. If the marks are 95, it will print this message “your marks on the rank” without a break. It continues to the next case and to the default case that is executed when the above cases are not met.

Example:

public class BreakDemo {

public static void main(string[] args) {

String str1 = args[0];

int marks = Integer.parselnt(str1);

switch(marks){

 case 95: System.out.println(“Your marks: “+marks” and rank is A”);

   break;

 case 80: System.out.println(“Your marks: “+marks” and rank is B”);

   break;

 case 70: System.out.println(“Your marks: “+marks” and rank is c”);

   break;

 default:

System.out.println(“Your marks: “+marks” and rank is FAIL”);

   break;

  }

 }

 }

Continue Statement

This example is to print odd numbers. The continue statement skips the iteration of for, while loops.

Example:

Continue-demo

public class ContinueDemo {

public static void main(string[] args) {

   for(int i=1;i<=10;i++){

   if(i%2 == 0) continue;

   System.out.println(“Odd number ” + i);

   }

  }

  }

Return Statement

The return statement is used to return the value from a method explicitly. The called class will process and transfer the control back to the caller of the method. The data type of the return value must match the type of methods declared return value. If a method is declared as void, it does not return a value.

Example:

Class Rectangle {

 int length;

 int breadth;

Void setDim(int le, int br){

 length = le;

 breadth = br;

 }

 int getArea() {

 return length * breadth;

 }

}

Connecting the Control Structure and connect the statements control structures in two ways, one is by stacking, and the other is by nesting.

Control Statement Stacking

The entry point of one activity diagram can be connected to the exit point of another. For example, a sequence statement and a selection statement can be combined through stacking.

Control Statement Nesting

An instruction or action in one control statement is replaced with another control statement. 

Also Read: Java Project Ideas & Topics

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