Decision-making in real life and decision-making in programming is somehow similar. In programming, there are some situations where we want a certain block of code to be executed to fulfill the condition.
Programming languages use control flow statements to control the flow of the execution of the program depends upon some conditions. It causes the flow of execution to advance and branch-based changes to state the program.
Java’s Selection statements:
- if
- if-else
- nested-if
- if-else-if
- switch-case
- jump – break, continue, return
The above statements help to control the flow of the program's execution based on the conditions known during the run time.
- if: if statement is the most straightforward method of decision-making statement. It is utilized to choose whether a specific statement or block of statements will be executed or not i.e assuming a specific condition is valid, a block of statement is executed in any case not.
Syntax:
Flowchart
Example
// Java program to illustrate If statement
class IfDemo
{
public static void main(String args[])
{
int i = 10;
if (i > 15)
System.out.println("10 is less than 15");
// This statement will be executed
// as if considers one statement by default
System.out.println("I am Not in if");
}
}
Output
I am Not in if
- if-else: The if statement alone reveals to us that if a condition is genuine it will execute a block of statements and if the condition is false it will not. Yet, consider the possibility that we need to accomplish something different if the condition is false. Here comes the else statement. We can utilize the else explanation with if statement to execute a block of code when the condition is false.
Syntax:
if (condition)
{
// Executes this block if
// condition is true
}
else
{
// Executes this block if
// condition is false
}
Flow chart
Example
// Java program to illustrate if-else statement
class IfElseDemo
{
public static void main(String args[])
{
int i = 10;
if (i < 15)
System.out.println("i is smaller than 15");
else
System.out.println("i is greater than 15");
}
}
Output
i is smaller than 15- nested-if: A nested if is an if the statement that is the objective of another if or else. Nested if statement implies and statement inside an if statement. Indeed, java permits us to settle if statement inside if statement. i.e, we can put an if statement inside another if statement.
Syntax
if (condition1)
{
// Executes when condition1 is true
if (condition2)
{
// Executes when condition2 is true
}
}
Flowchart
Example
// Java program to illustrate nested-if statement
class NestedIfDemo
{
public static void main(String args[])
{
int i = 10;
if (i == 10)
{
// First if statement
if (i < 15)
System.out.println("i is smaller than 15");
// Nested - if statement
// Will only be executed if statement above
// it is true
if (i < 12)
System.out.println("i is smaller than 12 too");
else
System.out.println("i is greater than 15");
}
}
}
Output
i is smaller than 15
i is smaller than 12 too- if-else-if ladder: Here, a user can settle on various options. The if statements are executed starting from the top. When one of the conditions controlling the if is valid, the statement related with that if is executed, and the rest of the ladder is circumvented. In the event that none of the conditions is valid, the last else statement will be executed.
Syntax
if (condition)
statement;
else if (condition)
statement;
.
.
else
statement;
Example
// Java program to illustrate if-else-if ladder
class ifelseifDemo
{
public static void main(String args[])
{
int i = 20;
if (i == 10)
System.out.println("i is 10");
else if (i == 15)
System.out.println("i is 15");
else if (i == 20)
System.out.println("i is 20");
else
System.out.println("i is not present");
}
}
Output
i is 20- jump: Java supports three jump statements: break, continue and return. These three statements transfer control to another part of the program.
- Break: In Java, the break is majorly used for:
- Terminate a sequence in a switch statement (discussed above).
- To exit a loop.
- Used as a “civilized” form of goto.
Using break to exit a Loop
Using break, we can force immediate termination of a loop, bypassing the conditional expression and any remaining code in the body of the loop.
Note: Break, when used inside a set of nested loops, will only break out of the innermost loop.
Example
// Java program to illustrate using
// break to exit a loop
class BreakLoopDemo
{
public static void main(String args[])
{
// Initially loop is set to run from 0-9
for (int i = 0; i < 10; i++)
{
// terminate loop when i is 5.
if (i == 5)
break;
System.out.println("i: " + i);
}
System.out.println("Loop complete.");
}
}
Output
i: 0
i: 1
i: 2
i: 3
i: 4
Loop complete.Using break as a Form of Goto
Java does not have a goto statement because it provides a way to branch in an arbitrary and unstructured manner. Java uses label. A Label is use to identifies a block of code.
Syntax
label:
{
statement1;
statement2;
statement3;
.
.
}
Example
class BreakLabelDemo
{
public static void main(String args[])
{
boolean t = true;
// label first
first:
{
// Illegal statement here as label second is not
// introduced yet break second;
second:
{
third:
{
// Before break
System.out.println("Before the break statement");
// break will take the control out of
// second label
if (t)
break second;
System.out.println("This won't execute.");
}
System.out.println("This won't execute.");
}
// First block
System.out.println("This is after second block.");
}
}
}
Output
Before the break.
This is after second block.Continue: Sometimes it is useful to force an early iteration of a loop. That is, you might want to continue running the loop but stop processing the remainder of the code in its body for this particular iteration. This is, in effect, a goto just past the body of the loop, to the loop’s end. The continue statement performs such an action.
Example
// Java program to illustrate using
// continue in an if statement
class ContinueDemo
{
public static void main(String args[])
{
for (int i = 0; i < 10; i++)
{
// If the number is even
// skip and continue
if (i%2 == 0)
continue;
// If number is odd, print it
System.out.print(i + " ");
}
}
}
Output
1 3 5 7 9Return: The return statement is used to explicitly return from a method. That is, it causes program control to transfer back to the caller of the method.
Example:
// Java program to illustrate using return
class Return
{
public static void main(String args[])
{
boolean t = true;
System.out.println("Before the return.");
if (t)
return;
// Compiler will bypass every statement
// after return
System.out.println("This won't execute.");
}
}
Output
Before the return.
){kind=link}
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