Java Fundamentals

JAVA FUNDAMENTALS……..
By- Shalabh Chaudhary [GLAU]
Initially Called Oak, Renamed as Java in 1995.
Java Bytecode(portable code or p-code) file (.class ) <- LISP lang(AI)
JVM reads byte codes and translates into machine code for execution.
Java is a compiled programming language.
Compiler - create .class file[contain bytecodes - is in binary form]
Compiler translate Java prog into intermed lang called bytecodes, understood by Java interpreter
Class loader - To read bytecodes from .class file into memory.
JVM uses a combination of interpretation and just-in-time compilation to translate
bytecodes into machine language.
Interpreted code runs much slower compared to executable code.
Bytecode enables Java run time system to execute programs much faster.
Java class file is designed for 
 Platform independence
 Network mobility
Compilation & Execution Order 
1. Java Source Code
2. Compilation
3. Class Loader
4. Byte Code Verification
5. Interpretation
6. Execution
JRE: Java Runtime Environment. It is basically the Java Virtual Machine where your
Java programs run on. It also includes browser plugins for Applet execution.
JDK: It's the full featured Software Development Kit for Java, including JRE, and the
compilers and tools (like JavaDoc, and Java Debugger) to create and compile programs.
JDK used to compile servlets also in JSP.
 Running Java programs => JRE
 For Java programming => JDK
PATH tells OS which directories(folders) to search for executable files. [Till /JDK/bin]
CLASSPATH is a parameter which tells the JVM or the Compiler, where to locate
classes that are not part of JDKS. [For Temporary setting <- In Environment Var]
The Java API 
 An Application Programming Interface, in the framework of java, is collection of
prewritten packages ,classes, and interfaces with the irrespective methods, fields and
constructors.
 The Java API, included with the JDK, describes the function of each of its components.

Java Keywords 
abstract break catch const
continue double extends float
for implements int native
new protected short super
switch throw try while
assert byte char
default else final
goto import interface
package public static
synchronized throws void
boolean case class
do enum finally
if instanceof long
private return strictfp
this transient volatile
Primitive DataTypes(8) 
DataType Size Default Value
1. Boolean 1 Bit false
2. Byte 1 Byte 0
3. Char 2 Bytes ‘u0000’
4. Short 2 Bytes 0
5. Int 4 Bytes 0
6. Float 4 Bytes 0.0f
7. Long 8 Bytes 0L
8. Double 8 Bytes 0.0d
 class Main {
public static void main(String ar[]) {
float f=1.2; // float f=(float)1.2; ‘or’ float f = 1.2f;
boolean b=1; // boolean b=true;
System.out.println(f);
System.out.println(b);
}
}
 class Test {
public static void main(String ar[]) {
double d=1.2D; // ‘or’ double d=1.2d; <= Both Correct.
System.out.println(d);
}
}

 class Test {
public static void main(String [ ] ar) {
int a=10,b=017,c=0X3A;
System.out.println(a+","+b+","+c); // >> 10,15,58
}
}
 Variable name can’t start with digits(0-9).
 class Test {
public static void main(String [] args) {
int x;
System.out.println(x); // >> = Error Variable initialization necessary
}
}
Types of Variables 
1. Local Variables:
 Tied to a method
 Scope of a local variable is within the method
2. Instance Variables (Non-Static):
 Tied to an object
 Scope of an instance variable is the whole class
3. Static Variables
 Tied to a class
 Shared by all instances of a class
Comparing Strings 
class Test {
public static void main(String [ ] args) {
String s1="Wipro";
String s2="Wipro";
System.out.println(s1.equals(s2)); // >> true
}
}
Logical Operators  [ Logical AND(&&) + OR(||) + NOT(!) ]
class Test{
public static void main(String[] args){
boolean a = true;
boolean b = false;
System.out.println(a&&b); // >> false <= Both true  true

System.out.println(a||b); // >> true <= Either/Both true  true
System.out.println(!(a && b)); // >> true <= Reverse value of bool expr
}
}
Shift Operators  [ Right(>>) + Left(<<) Shift ]
1. (>>) operator = To divide no. in multiples of 2.
Eg: int x = 16;
x = x>>3;
Output: 16/2^3  16/8  2
2. (<<) operator = To multiply no. in multiples of 2.
Eg: int y = 8;
y = y<<4;
Output: 8*2^4  8*16  128
Bitwise Operator [ Bitwise AND(&) + Inclusive OR(|) + Exclusive OR(^) ]
First Convert in Binary Form then,
1. & = Both bits are 1 => 1
2. | = EitherBoth bits 1 => 1
3. ^ = Different bits => 1
Passing command line arguments 
#1. Write a Program that accepts two Strings as command line arguments
and generate the output in a specific way as given below.
Example:
If the two command line arguments are Wipro and Bangalore then the
output generated should be Wipro Technologies Bangalore.
If the command line arguments are ABC and Mumbai then the output
generated should be ABC Technologies Mumbai
[Note: It is mandatory to pass two arguments in command line]
>>
public class CmdLineString {
public static void main(String[] args) {
System.out.println(args[0]+" Technologies "+args[1]);
}
}

#2. Write a Program to accept a String as a Command line argument and
the program should print a Welcome message.
Example :
C:> java Sample John
O/P Expected : Welcome John
>>
public class WelcomeMsg {
System.out.println("Welcome "+args[0]);
}
}
#3. Write a Program to accept two integers through the command line
argument and print the sum of the two numbers
Example:
C:>java Sample 10 20
O/P Expected : The sum of 10 and 20 is 30
Write a Program to accept two integers through the command line
argument and print the sum of the two numbers
Example:
C:>java Sample 10 20
O/P Expected : The sum of 10 and 20 is 30
>>
public class CmdLineValue {
int n1 = Integer.parseInt(args[0]);
int n2 = Integer.parseInt(args[1]);
System.out.println("The sum of 10 and 20 is "+(n1+n2));
}
}

Flow Control 
1. Selection stmt. [ if + if..else + switch ]
2. Iteration stmt. [ for + while + do..while ]
3. Jumping stmt. [ break + continue + return ]
 public class DoWhile {
public static void main(String[]args){
int i=5;
do{
System.out.println("i:"+i); // >> 5
i++; // i=6
}while(i<5); // cond. False 6<5
}
}
 class BreakContinue {
public static void main(String args[]){
for(int i=1;i<=5;i++) {
if(i==4) break; // execution stops when i becomes 4
System.out.println(i); // >> 1 2 3
}
for(int i=1;i<=5;i++) {
if(i==1) continue; // execution skip when i becomes 1
System.out.println(i); // >> 2 3 4 5
}
}
}
 class Sample {
public static void main(String[]args) {
while(false) // while(true) then Infinite looping
System.out.print("whileloop"); // >> Error - Unreachable stmt.
}
}
 public class Sample {
for( ; ; )
System.out.println("For Loop"); // Infinite Looping
}
}

#1. Write a program to check if the program has received command line
arguments or not. If the program has not received the values then
print "No Values", else print all the values in a single line
separated by ,(comma).
Eg1) java Example
O/P: No values
Eg2) java Example Mumbai Bangalore
O/P: Mumbai,Bangalore
[Note: You can use length property of an array to check its length
>>
public class CountCmdLineArg {
if(args.length==0)
System.out.println("No Values");
else {
for(int i=0;i<args.length;i++) // for(String values:args)
System.out.print(args[i]+", "); // S.o.p(values+", ");
}
}
}
#2. Initialize two character variables in a program and display the
characters in alphabetical order.
Eg1) if first character is s and second is e
O/P: e,s
Eg2) if first character is a and second is e
O/P:a,e
>>
import java.util.Scanner;
public class AlphabetOrder {
Scanner scan=new Scanner(System.in);

char c1=scan.next().charAt(0);
char c2=scan.next().charAt(0);
if(c1>c2)
System.out.print(c2+","+c1);
else
System.out.println(c1+","+c2);
}
}
 next() function returns the next token/word in the input as a string and
 charAt(0) function returns the first character in that string.
#3. Initialize a character variable in a program and if the value is
alphabet then print "Alphabet" if it’s a number then print "Digit" and
for other characters print "Special Character"
>>
public class CheckAplhaDigSpec {
char c=scan.next().charAt(0);
if((c>='a' && c<='z') || (c>='A' && c<='Z'))
System.out.println("Alphabet");
else if(c>='0' && c<='9')
System.out.println("Digit");
else
System.out.println("Special Sym");
}
}

#4. WAP to accept gender ("Male" or "Female") & age (1-120) from
command line arguments and print the percentage of interest based on
the given conditions.
Interest == 8.2%
Gender ==> Female
Age ==>1 to 58
Interest == 7.6%
Gender ==> Female
Age ==>59 -120
Interest == 9.2%
Gender ==> Male
Age ==>1-60
Interest == 8.3%
Gender ==> Male
Age ==>61-120
>>
public class GenderInterest {
String gender=args[0];
int age=Integer.parseInt(args[1]);
if(gender.equalsIgnoreCase("Female")) { // Compare Strings
if(age>=1 && age<=58)
System.out.println("Interest= 8.2%");
else if(age>58 && age<=120)
}
else {
if(age>=1 && age<=60)
else if(age>60 && age<=120)
} }
}

#5. Write a program to convert from upper case to lower case and vice
versa of an alphabet and print the old character and new character as
shown in example (Ex: a->A, M->m).
>>
public class Sample {
char c=scan.next().charAt(0);
int temp;
/*if (Character.isLowerCase(c))
System.out.println(c+"->"+Character.toUpperCase(c));
else
System.out.println(c+"->"+Character.toLowerCase(c)); */
if(c>='a' && c<='z') {
System.out.print(c+"->");
temp=(int)c;
c=(char)(temp-32);
System.out.println(c);
}
else {
System.out.print(c+"->");
temp=(int)c;
c=(char)(temp+32);
System.out.println(c);
}
}
}

#6. Write a program to print the color name, based on color code. If
color code in not valid then print "Invalid Code". R->Red, B->Blue, G-
>Green, O->Orange, Y->Yellow, W->White.
>>
public class ColorCode {
char ch=args[0].charAt(0); // Input character using Cmd Line
switch(ch) {
case 'R': System.out.println("R->Red");
break;
case 'B': System.out.println("B->Blue");
break;
case 'G': System.out.println("G->Green");
break;
case 'O': System.out.println("O->Orange");
break;
case 'Y': System.out.println("Y->Yellow");
break;
case 'W': System.out.println("W->White");
break;
default: System.out.println("Invalid");
}
}
}

#7. Write a program to check if a given number is prime or not
>>
public class CheckPrime {
int n=scan.nextInt();
int count=0;
for(int i=1;i<=n;i++) {
if(n%i==0)
count++;
}
scan.close();
if(count==2)
System.out.println("prime");
else
System.out.println("Not prime");
}
}
#8. Write a Java program to find if the given number is prime or not.
Example1:
C:>java Sample
O/P Expected : Please enter an integer number
Example2:
C:>java Sample 1
O/P Expected : 1 is neither prime nor composite
Example3:
C:>java Sample 0
O/P Expected : 0 is neither prime nor composite
Example4:

C:>java Sample 10
O/P Expected : 10 is not a prime number
Example5:
C:>java Sample 7
O/P Expected : 7 is a prime number
>>
public class CheckPrimeComp {
int n=Integer.parseInt(args[0]);
int c=0;
if(args.length==0)
System.out.println("Please Enter int number");
else if(n==0 || n==1)
System.out.println(n+" is neither prime nor composite");
else {
for(int i=1;i<=n;i++) {
if(n%i==0)
c++;
}
}
if(c==2)
System.out.println(n+" is a Prime number");
else
System.out.println(n+" is not a Prime number");
}
}

#9. Write a program to print prime numbers between 10 and 99.
>>
public class PrimeBetween {
int temp,i;
for(i=10;i<=99;i++) {
temp=0;
for(int j=2;j<i;j++) {
if(i%j==0) {
temp=1;
break;
}
}
if(temp==0)
System.out.println(i);
}
}
}
#10. Write a program to add all the values in a given number and
print. Ex: 1234->10
>>
public class AddDigitNum {
int n=12345;
int rem,val=0;
while(n!=0) {
rem=n%10;
val=val+rem;
n=n/10;

}
System.out.println(val);
}
}
#11. Write a program to print * in Floyds format (using for and while
loop)
*
* *
* * *
Example1:
C:>java Sample
O/P Expected : Please enter an integer number
Example1:
C:>java Sample 3
O/P Expected :
*
* *
* * *
>>
public class FloydsForm {
for(int i=0;i<n;i++) {
for(int j=0;j<=i;j++) {
System.out.print("* ");
}
System.out.println();
}
}
}

#12. Write a program to reverse a given number and print
Eg1)
I/P: 1234
O/P:4321
Eg2)
I/P:1004
O/P:4001
>>
public class ReverseNum {
int n=12345;
int rem;
while(n!=0) {
rem=n%10;
System.out.print(rem);
n=n/10;
}
}
}
#13. Write Java program to find if given number is palindrome or not
Example1:
C:>java Sample 110011
O/P Expected: 110011 is a palindrome
Example2:
C:>java Sample 1234
O/P Expected: 1234 is not a palindrome
>>
public class PalindromeNum {

int temp=n;
int cur=0,rem;
while(temp!=0) {
rem=temp%10;
cur=cur*10+rem;
temp=temp/10;
}
if(n==cur)
System.out.println(n+" is a Palindrome");
else
System.out.println(n+" is not a Palindrome");
}
}
#14. Write a program to print first 5 values which are divisible by 2,
3, and 5.
>>
public class First5Div {
int count=0,i=1;
while(count<5) {
if(i%2==0 && i%3==0 && i%5==0) {
System.out.println(i);
count++;
}
i++;
}
} }

Handling Arrays 
An array is a container object that holds a fixed number of values of a single type.
Syntax:
int[] ar = new int[ar_size]; // new allocates mem. for all ar int
 Example using foreach Loops :
public class UseForEach {
double[] ar = {1.9, 2.9, 3.4, 3.5};
for (double ele:ar)
System.out.println(ele); // Print all elements
}
}
 Passing Arrays to Methods :
mthdName(new int[]{3, 1, 2, 6, 4, 2});
 To Find Array Size :
int ar_len = ar.length;
Array Copy 
arraycopy static method from System class -To copy arr ele from one arr
to another array.
Syntax :
public static void arraycopy(obj src, int srcIndx, obj dest, int destIndx, src.length)
 Eg:
int[] src = {1,2,3,4,5,6};
int[] dest = newint[10];
System.arraycopy(src,0,dest,0,src.length);
Two-Dimensional Arrays 
Two-dimensional arrays are arrays of arrays.
 Initialization :
int[][] ar = new int[row_size][col_size];
 row_size is mandatory, col_size can be empty else get err.
 Eg:
1. int[][] y = { {1,2,3}, {4,5,6}, {7,8,9} };
2. int[][] y = new int[][] { {1,2,3}, {4,5,6}, {7,8,9} };

OUTPUT BASED -
int[] a = new int[5]{1,2,3,4}; // INVALID - Highlighted wrong
int a[5] = new int[5]; // INVALID - Highlighted wrong
 class Test {
while(false)
System.out.println("while loop"); // Err – Unreachable stmt.
}
}
 class Test {
int[] x=new int[10];
System.out.println(x[4]); // Output- 0 {Every ele of arr=0}
}
}
 class Test {
int x[][]=new int[10] [ ];
System.out.println(x[4][0]); // Output- Run Time Error NullPtrExcp
}
}
#1. Write a program to initialize an integer array and print the sum
and average of the array
>>
public class ArraySumAvg {
int ar[]=new int[]{1,2,3,4,5};
int sum=0;
float avg=0.0f;
for(int ele:ar)
sum=sum+ele;
avg=(float)sum/ar.length;
System.out.println(sum+" "+avg);
}
}

#2. Write a program to initialize an integer array & find the maximum
and minimum value of an array
>>
Import java.util.Scanner;
public class MaxMin {
//System.out.println("Enter Size of Array");
int ar[]=new int[n];
//System.out.println("Enter Array Ele");
for(int i=0;i<n;i++)
ar[i]=scan.nextInt();
int max=ar[0];
int min=ar[0];
for(int i:ar)
if(i>max)
max=i;
else if(i<min)
min=i;
System.out.println("Max "+max);
System.out.println("Min "+min);
}
}

#3. WAP to initialize integer array with values & check if given no is
present in the array or not. If the number is not found, it will print
-1 else it will print the index value of the given number in array.
Ex1) Array elements are {1,4,34,56,7} and the search element is 90
O/P: -1
Ex2) Array elements are {1,4,34,56,7} and the search element is 56
O/P: 4
>>
public class FindEle {
//System.out.println("Enter no. of Ele in Array");
System.out.println("Enter ele to Search");
int ele=scan.nextInt();
int flag=0,i;
for(i=0;i<n;i++)
if(ar[i]==ele) {
flag=1;
break;
}
if(flag==1)
System.out.println(ele+" at pos "+(i+1));
else
System.out.println(-1);
}
}

#4. Initialize an integer array with ascii values and print the
corresponding character values in a single row.
>>
public class ASCII2Symb {
//System.out.println("Enter no. of Ele in Array");
char ch=0;
int i;
for(i=0;i<n;i++) {
ch=(char)ar[i];
System.out.print(ar[i]+"->"+ch+", ");
}
}
}
#5. Write a program to find the largest 2 numbers and the smallest 2
numbers in the given array
>>
public class Larget2Smallest {

int max1,max2,min1,min2;
max1=max2=Integer.MIN_VALUE;
min1=min2=Integer.MAX_VALUE;
if(ar[i]>max1) {
max2=max1;
max1=ar[i];
}
else if(ar[i]>max2)
max2=ar[i];
}
System.out.println("Largest: "+max1+" & "+max2);
if(ar[i]<min1) {
min2=min1;
min1=ar[i];
}
else if(ar[i]<min2)
min2=ar[i];
}
System.out.println("Smallest: "+min1+" & "+min2);
}
}
 Integer.MIN_VALUE specifies - Integer variable can’t store any value below this limit i.e., limit of int.
 Integer.MAX_VALUE – Max value a variable can hold.

Bubble Sort
Bubble Sort is the simplest sorting algorithm that works by repeatedly swapping the
adjacent elements if they are in wrong order.
Eg:
I-Pass:
( 5 1 4 2 8 ) –> ( 1 5 4 2 8 ), Compares first two elements, and swaps since 5 > 1.
( 1 5 4 2 8 ) –> ( 1 4 5 2 8 ), Swap since 5 > 4
( 1 4 5 2 8 ) –> ( 1 4 2 5 8 ), Swap since 5 > 2
( 1 4 2 5 8 ) –> ( 1 4 2 5 8 ), No swap.
II-Pass:
Second Pass:
( 1 4 2 5 8 ) –> ( 1 4 2 5 8 )
( 1 4 2 5 8 ) –> ( 1 2 4 5 8 ), Swap since 4 > 2
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
Now, the array is already sorted, but our algorithm does not know if it is completed. The
algorithm needs one whole pass without any swap to know it is sorted.
III-Pass:
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
( 1 2 4 5 8 ) –> ( 1 2 4 5 8 )
 Algorithm:
for(int i=0;i<n-1;i++)
for(int j=0;j<n-i-1;j++)
if(ar[j]>ar[j+1]) {
int temp=ar[j];
ar[j]=ar[j+1];
ar[j+1]=temp;
}
#6. Write a program to initialize an array and print them in a sorted
fashion.
>>
public class ArraySort {

if(ar[j]>ar[j+1]) {
int temp=ar[j];
ar[j]=ar[j+1];
ar[j+1]=temp;
}
System.out.print(ar[i]+" ");
}
}
 Arrays.sort(ar); ==> To sort any Array. ar-Array to sort.
7
Write a program to remove the duplicate elements in an array and
print
Eg) Array Elements--12,34,12,45,67,89
O/P: 12,34,45,67,89
>>
public class RemoveDuplictes {

if(ar[j]>ar[j+1]) {
int temp=ar[j];
ar[j]=ar[j+1];
ar[j+1]=temp;
}
System.out.println("Sorted Array:");
for (int i=0; i<n; i++)
int[] temp = new int[n];
int j = 0;
for (int i=0; i<n-1; i++)
if (ar[i] != ar[i+1])
temp[j++] = ar[i]; // Store ele if curr_ele!=next_ele
temp[j++] = ar[n-1]; // Store last_ele unique/repeated, not stored prev
// Modify original array
for (int i=0; i<j; i++)
ar[i] = temp[i];
System.out.println("nArray without Duplicates:");
for (int i=0; i<j; i++)
}
}

8
Write a program to print the element of an array that has occurred
the highest number of times
Eg) Array -> 10,20,10,30,40,100,99
O/P:10
>>
import java.util.Arrays;
public class HighestFrequency {
Arrays.sort(ar);
int max_count=1,cur_count=1;
int res=ar[0];
if(ar[i]==ar[i-1])
cur_count++;
else {
if(cur_count>max_count) {
max_count=cur_count;
res=ar[i-1];
}
cur_count=1;
}
if(cur_count>max_count) {
max_count=cur_count;

res=ar[n-1];
}
System.out.println("Max Occured ele: "+res);
}
}
 Efficient solution – If Use Hashing - O(n). [For Above Q.]
9
Write a program to print the sum of the elements of the array with
the given below condition. If the array has 6 and 7 in succeeding
orders, ignore 6 and 7 and the numbers between them for the
calculation of sum.
Eg1) Array Elements - 10,3,6,1,2,7,9
O/P: 22
[i.e 10+3+9]
Eg2) Array Elements - 7,1,2,3,6
O/P:19
Eg3) Array Elements - 1,6,4,7,9
O/P:10
>>
public class SumExceptBetween67 {
int flag=0;
int sum=0;
for(int i:ar) {

if(i==6)
flag=1;
if(flag==1) {
if(i==7)
flag=0;
continue; // Above code to skip val b/w 6 to 7
}
else {
// If first get 7 then add 6, next time 6 come then skipped from above code
if(i==7)
sum+=i+6;
else
sum+=i;
}
}
System.out.println("Total: "+sum);
}
}
#10. Write a program to reverse the elements of a given 2*2 array.
Four integer numbers needs to be passed as Command Line arguments.
Example1:
C:>java Sample 1 2 3
O/P Expected : Please enter 4 integer numbers
Example2:
C:>java Sample 1 2 3 4
O/P Expected :
The given array is :
1 2

3 4
The reverse of the array is :
4 3
2 1
1 2 3 4
5 6 7 8
9 10 11 12
>>
#11. Write a program to find greatest number in a 3*3 array. The
program is supposed to receive 9 integer numbers as command line
arguments.
Example1:
C:>java Sample 1 2 3
O/P Expected : Please enter 9 integer numbers
Example2:
C:>java Sample 1 23 45 55 121 222 56 77 89
O/P Expected :
The given array is :
1 23 45
55 121 222
56 77 89
The biggest number in the given array is 222
>>
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