Write about Decision making and Branching statements in Java with Examples?
https://www.computersprofessor.com/2017/01/write-about-decision-making-and.html
Decision making
and Branching statements:
A java program
is a set of statements which are normally executed sequentially same in the
order in which they appear.
When a program
breaks the sequential flow and jumps to another part of the code, it is
called branching. When the branching is based on a particular condition it is
known as conditional branching. If branching takes place without any decision
it is known as unconditional branching.
Decision
making statements are
1. If
2. switch
3. conditional
operator statement
Decision making
with if statement :
The if statement if a powerful decision
making statement and in used to control the flow of execution of statements.
It is basically a two way decision statements .
if(test
expression)
it allows the
computer to evaluate the expression first and then depending on whether the
value of the expression is true or false, it transfers the control to a
particular statement.
for eg:
if (bank
balance is zero)
borrow money;
The if
statement may be implemented in different forms depending on the complexity of
conditions to be tested.
®
simple if statement
® if
else statement
®
nested if statement
®
else if ladder
Simple if
statement:
The general
form of a simple if statement is:
if(test
expression)
{
Statement–block;
}
Statement x;
The statement
block may be a single statement (or) a group of statement.
If the text
expression is true the statement block will be executed, otherwise the
statement block will be stopped and the execution will jump to the statement
x.
Eg :
if (
category==sports)
{
marks=marks+bonus;
}
System.out.println
(“marks”);
If else
statement:
The if else statement is an extension of the
simple if statement.
The general
form is
if(test expression)
{
True–block
statement;
}
else
{
False–block
statement;
}
Statement–x;
If the test
expression is true then the true block statements immediately following the
if statement are executed otherwise the false block statements are executed.
In either case true block (or) false block will be executed not both.
In both the
cases the control is transferred subsequently for the statement x.
Eg:
if (code==1)
boy=boy+1;
else
girl=girl+1;
// count the
even & odd number in a list.
Eg:
class Test
{
public static void main (String arg[ ])
{
int number[
]={50,65,80,15,23,18};
int even=0,
odd=0;
for(int i=0; i
|
{
if(number[i] %
2==0)
{
even=even+1;
}
else
{
odd=odd+1;
}
}
System.out.println
(“even numbers”+even+”odd numbers”+odd);
}
}
Nested if else
statement:
When a series
of decisions are involved we may have to use more than and if else statement
in nested form as follows.
if(test
condition 1)
{
if(test
condition 2)
{
Statement -1;
}
else
{
Statement -2;
}
}
else
{
Statement-3;
}
Statement-x;
If the
condition 1 is true stamen 3 will be executed otherwise it continuous to
perform the second test. If the condition 2 is true the statement 1 will be
executed otherwise the statement 2 will be evaluated and then the control is
transferred to the statement x.
class Largest
{
public static
void main(String a[ ])
{
int a, b, c;
a=100;
b=150;
c=125;
if(a > b)
{
if (a > c)
System.out.println
(“a is big”+a);
else
System.out.
println(“c is big”+c);
}
else
{
if(b > c)
System.out.println
(“b is big”+b);
else
System.out.println
(“c is big”+c);
}
}
}
Else if ladder:
There is
another way of putting if’s together when multipath decisions are involved. A
multipath decision is a chain of its in which the statement associated with
each else is on if. It takes the following general form.
if(condition
1)
Statement -1;
else if
(condition 2)
Statement -2;
else if
(condition 3)
Statement -3;
-------------
-------------
else
if(condition n)
Statement-n;
else
Default
statement;
Statement x;
The construct
is known as the else if ladder. The conditions are evaluated from the top to down
words as soon as the true condition is found. The stamen associated with it
is executed and the control is transferred to the statement x. (skipping the
rest of the ladder) . When all the n
controls become false then the final else contains the default statement will
be executed.
class Sample
{
public static
void main(String a[ ])
{
int roll_number
[ ]={101, 102, 103, 104, 105};
int number [ ]
={85, 72, 35, 68, 50};
for(int i=0; i
< roll_number. Length ;i++)
{
if(marks[i]
> 79)
System.out.println(rollnumber[i]+”distension”);
else if
(marks[1] >> 59)
System.out.println
(rollnumber[i]+”I class”);
else if(marks[i]
> 49)
System.out.println
(rollnumber[i]+”II class”);
else
System.out.println
(rollnumber[i]+”fail”);
}
}
}
Switch :
Java is a
built in multi-way decision statement known as switch. The switch statement
tests the value of a given variable (or expression) against a list of case
values and when a match is found a block of statements associated with that
case is executed. The general form of the switch statement is as shown below.
switch(expression)
{
case value-1:
Block-1;
break;
case value-2:
Block-2;
break;
--------------
-------------
case value-n:
Block-n;
break;
default:
Default
statement;
}
Statement x;
The expression
is an integer expression or characters. Value-1, value-2 and ….. are constants(or) constant expressions and are
known as case labels. Each of these values should be unique with in a switch
statement , block-1, block-2 are statement lists and may contain 0 or more statements . there is no need to put
braces around these blocks, but it is important to note that case levels and with
a colon(:).
The break
statement at the end of each block. End of particular case and causes on
exist from the switch statement, transferring the control to the statement x,
following the switch.
The default is
an optional case. When present it will be executed if the value of the
expression doesn’t match with any of the case values.
Eg :
import
java.io.*;
class
Arthemtic
{
public static
void main (String a[ ] ) throwsIOException
{
BufferedReader
br=new BufferedReader(new InputStreamReader(System.in));
char choice;
int a=10,
b=20, c;
System.out.println
(“1:addition”);
System.out.println
(“2:subtraction”);
System.out.println
(“3:multiplication”);
System.out.println
(“4:divison”);
System.out.println
(“enter your choice”);
choice=br.read(
);
switch(choice)
{
case 1: c=a+b;
System.out.
println(“addition value is”+c);
break;
case 2: c=a–b;
System.out.println
(“sub value is “+c);
break;
case 3: c=a*b;
System.out.println
(“mul value is”+c);
break;
case 4: c=a/b;
System.out.println
(“division value is”+c);
break;
default:
System.out.println(“enter
invalid choice”);
}
}
}
The ?: operator (conditional operator)
:
This operator is useful for making two
way decisions.
This operator
is a combination of :? and takes three operands. This operator is popularly
known as the conditional operator.
The general
form of the conditional operator is as
follows :
Conditional
expression ? exp 1 : exp 2 ;
The conditional
expression is evaluated first if the result is true expression 1 is evaluated
and it is the result of total statements. Otherwise expression 2 is evaluated
and its value is returned.
For eg:
if(x < 0)
flag=0;
else
flag=1;
Can be written
as flag=(x<0 0:1="" o:p="">
