Difference between Post Increment (n++) and Pre Increment (++n)
Post Increment (n++): It increases the value of variable by 1 after execution of the statement.
Pre Increment (++n): It increases the value of variable by 1 before execution of the statement.
| Program |
Output |
class Demo
{
public static void main(String args[])
{
int n=10;
System.out.println(n);
System.out.println(n++);
System.out.println(n);
}
}
|
10
10
11
|
| Program |
Output |
class Demo
{
public static void main(String args[])
{
int n=10;
System.out.println(n);
System.out.println(++n);
System.out.println(n);
}
}
|
10
11
11
|
|
| |
Prime Number
Logic: Prime Number are divisible by itself only.
| Not divisible by any Number |
Divisible by 2 ...no need to check further |
Divisible by 3 ...no need to check further |
7%2=1
7%3=1
7%4=3
7%5=2
7%6=1 |
8%2=0
8%3=
8%4=
8%5=
8%6=
8%7= |
9%2=1
9%3=0
9%4
9%5
9%6
9%7
9%8 |
| Numbers are not divisible by more than half of the number |
No need to check upto 6 check upto 3 only
|
No need to check upto 7 check upto 4 only |
No need to check upto 8 check upto 4 only |
| Program |
Output |
//Note: Scanner class work with JDK1.5 or above
import java.util.*;
class Prime
{
public static void main(String args[])
{
int n, i, res;
boolean flag=true;
Scanner scan= new Scanner(System.in);
System.out.println("Please Enter a No.");
n=scan.nextInt();
for(i=2;i<=n/2;i++)
{
res=n%i;
if(res==0)
{
flag=false;
break;
}
}
if(flag)
System.out.println(n + " is Prime Number");
else
System.out.println(n + " is not Prime Number");
}
}
|
Please Enter a No.: 7
7 is Prime Number
|
|
| |
Fibonacci Series ( 1 1 2 3 5 8 13...)
Logic: Sum of previous two numbers will give us next number.
| prev |
next |
sum |
| |
shifted to prev |
shifted to next |
| 1 |
1 |
2 |
| 1 |
2 |
3 |
| 2 |
3 |
5 |
| 3 |
5 |
8 |
| 5 |
8 |
13 |
| 8 |
13 |
... |
| 13 |
... |
... |
| prev will give you fibonacci series |
| Program |
Output |
class Fibonacci
{
public static void main(String args[])
{
int prev, next, sum, n;
prev=next=1
for(n=1;n<=10;n++)
{
System.out.println(prev);
sum=prev+next;
prev=next;
next=sum;
}
}
}
|
1
1
2
3
5
8
13
... |
|
| |
Sum of 1st 10 Natural Numbers
Logic: Sum of previous two numbers will give us next number.
| sum |
n |
sum |
| sum+n |
|
| 0 |
1 |
1 |
| 1 |
2 |
3 |
| 3 |
3 |
6 |
| 6 |
4 |
10 |
| 10 |
5 |
15 |
| 15 |
6 |
21 |
| 21 |
7 |
28 |
| 28 |
8 |
36 |
| 36 |
9 |
45 |
| 45 |
10 |
55 |
| Program |
Output |
class Sum10
{
public static void main(String args[])
{
int n, sum=0;
for(n=1;n<=10;n++)
{
sum+=n; //or sum=sum+n;
}
System.out.println(sum);
}
}
|
55 |
|
| |
Sum of Square of 1st 10 Natural Numbers
Logic: Sum of previous two numbers will give us next number.
| sum |
n*n |
sum |
| sum+n*n |
|
| 0 |
1*1 |
1 |
| 1 |
2*2 |
5 |
| 5 |
3*3 |
14 |
| 14 |
4*4 |
30 |
| 30 |
5*5 |
55 |
| 55 |
6*6 |
91 |
| 91 |
7*7 |
140 |
| 140 |
8*8 |
204 |
| 204 |
9*9 |
285 |
| 285 |
10*10 |
385 |
| Program |
Output |
class SumSq10
{
public static void main(String args[])
{
int n, sum=0;
for(n=1;n<=10;n++)
{
sum+=n;*n //or sum=sum+n;*n
}
System.out.println(sum);
}
}
|
385 |
|
| |
Factorial
Logic: Factorial of 5 = 5 x 4 x 3 x 2 x 1
| prod |
n |
prod |
| prod*n |
|
| 1 |
5 |
5 |
| 5 |
4 |
20 |
| 20 |
3 |
60 |
| 60 |
2 |
120 |
| 120 |
1 |
120 |
| Program |
Output |
//Note: Scanner class work with JDK1.5 or above
import java.util.*;
class Factorial
{
public static void main(String args[])
{
int n, i, prod=1;
Scanner scan= new Scanner(System.in);
System.out.println("Please Enter a No.");
n=scan.nextInt();
for(i=n;i>=1;i--)
{
prod*=i; //prod=prod*i;
}
System.out.println("Factorial of " + n + " is " + prod);
}
}
|
Please Enter a No.: 5
Factorial of 5 is 120
|
|
| |
Biggest of 3 Numbers using Logical Operators
| Program |
Output |
//Note: Scanner class work with JDK1.5 or above
import java.util.*;
class Biggest3
{
public static void main(String args[])
{
int n1, n2, n3, big;
Scanner scan= new Scanner(System.in);
System.out.println("Please Enter No 1: ");
n1=scan.nextInt();
System.out.println("Please Enter No 2: ");
n2=scan.nextInt();
System.out.println("Please Enter No 3: ");
n3=scan.nextInt();
if(n1>n2 && n1>n3)
big=n1;
else if(n2>n1 && n2>n3)
big=n2;
else
big=n3;
System.out.println("Biggest No: " + big);
}
}
|
Please Enter No 1: 5
Please Enter No 2: 23
Please Enter No 3: 14
Biggest No: 23
|
|
| |
Biggest of 3 Numbers using Nested If
| Program |
Output |
//Note: Scanner class work with JDK1.5 or above
import java.util.*;
class Biggest3
{
public static void main(String args[])
{
int n1, n2, n3, big;
Scanner scan= new Scanner(System.in);
System.out.println("Please Enter No 1: ");
n1=scan.nextInt();
System.out.println("Please Enter No 2: ");
n2=scan.nextInt();
System.out.println("Please Enter No 3: ");
n3=scan.nextInt();
if(n1>n2)
{
if(n1>n3)
big=n1;
else
big=n3;
}
else
{
if(n2>n3)
big=n2;
else
big=n3;
}
System.out.println("Biggest No: " + big);
}
}
|
Please Enter No 1: 5
Please Enter No 2: 23
Please Enter No 3: 14
Biggest No: 23
|
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| |
Swap 2 Numbers using 3rd Variable
Logic:
| n1 |
n2 |
temp |
| 5 |
23 |
0 |
| 5 |
23 |
5 |
| 23 |
23 |
5 |
| 23 |
5 |
5 |
| Program |
Output |
//Note: Scanner class work with JDK1.5 or above
import java.util.*;
class Swap
{
public static void main(String args[])
{
int n1, n2, temp;
Scanner scan= new Scanner(System.in);
System.out.println("Please Enter No 1: ");
n1=scan.nextInt();
System.out.println("Please Enter No 2: ");
n2=scan.nextInt();
temp=n1;
n1=n2;
n2=temp;
System.out.println("First No: " + n1);
System.out.println("Second No: " + n2);
}
}
|
Please Enter No 1: 5
Please Enter No 2: 23
First No: 23
Second No: 5
|
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| |
Swap 2 Numbers without using 3rd Variable
Logic:
| n1 |
n2 |
| 10 |
5 |
| 15 |
5 |
| 15 |
10 |
| 5 |
10 |
| Program |
Output |
//Note: Scanner class work with JDK1.5 or above
import java.util.*;
class Swap
{
public static void main(String args[])
{
int n1, n2, temp;
Scanner scan= new Scanner(System.in);
System.out.println("Please Enter No 1: ");
n1=scan.nextInt();
System.out.println("Please Enter No 2: ");
n2=scan.nextInt();
n1=n1+n2;
n2=n1-n2;
n1=n1-n2
System.out.println("First No: " + n1);
System.out.println("Second No: " + n2);
}
}
|
Please Enter No 1: 10
Please Enter No 2: 5
First No: 5
Second No: 10
|
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| |
Sum of Digits
Logic: 513 -> 5+1+3=9
| n |
res |
n |
sum |
| 513 |
|
|
0 |
| 513%10 |
3 |
|
3 |
| 513/10 |
|
51 |
3 |
| |
|
|
|
| 51%10 |
1 |
|
4 |
| 51/10 |
|
5 |
4 |
| |
|
|
|
| 5%10 |
5 |
|
9 |
| 5/10 |
|
0 |
9 |
| Program |
Output |
//Note: Scanner class work with JDK1.5 or above
import java.util.*;
class SumDigits
{
public static void main(String args[])
{
int n, res;
Scanner scan= new Scanner(System.in);
System.out.println("Please Enter No.: ");
n1=scan.nextInt();
while(n>0)
{
res=n%10;
n=n/10;
sum+=res; //sum=sum+res;
}
System.out.println("Second No: " + n2);
}
}
|
Please Enter No 1: 10
Please Enter No 2: 5
First No: 5
Second No: 10
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