JAVA
Print
normal option
System.out.print(”hello world”);
System.out.print(”hello world”);
System.out.print(”hello world2”);
to avoid this you can use println or else \n
System.out.println("hello world");
System.out.print("hello world");
Getting input from a user
First step : import java.util
import java.util.*
Second step : Scanner
Scanner sc = new Scanner(System.in);
Third step : adding sc.next
String name = sc.next();
JAVA
1
int a = sc.nextInt();
double b = sc.nextDouble();
Conditional statements
basic if else
if (condition){
statement;
}
else {
statement;
}
example (if the number is odd or even):
import java.util.*;
class Condition {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("enter number:");
int a=sc.nextInt();
if (a%2==0){
System.out.print("the given number is even");
}
else{
System.out.print("the given number is odd");
}
}
}
nested else:
JAVA
2
if (condition){
statement;
}
else {
if (condition)
{
statement;
}
else
{
statement;
}
}
Else if :
if (condition)
{
statement;
}
else if (condition)
{
statement;
}
else
{
statement;
}
Switch statement
switch (variable){
case 1 : statement 1;
break;
case 2 : statement 2;
break;
case 3 : statement 3;
break;
default : statement 4;
}
JAVA
3
import java.util.*;
class Condition {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("enter any string:");
String a = sc.next();
switch (a){
case "hello" : System.out.print("hello world");
break;
case "name" : System.out.print("Vaibhav");
break;
case "subject" : System.out.print("Java");
break;
default : System.out.print("enter hello ,name or subject");
}
}
}
Example
Loops
For loop
syntax
for (initialisation;condition;updation){
statement;
}
Sample code
import java.util.*;
class Condition {
public static void main(String[] args) {
JAVA
4
for (int i=0;i<3;i++)
{
System.out.print("hello world\n");
}
}
}
infinite loop in for
for (int i = 0 ; ; i++){
statement;
}
While loop
Syntax
while (condition){
statement;
}
Sample code
import java.util.*;
class Condition {
public static void main(String[] args) {
int i = 0;
while (i<3){
System.out.println("hello world");
i++;
}
}
}
Do while loop
Syntax
do{
statement;
JAVA
5
}while (condition);
//note in do while it will first execute the statement and then check the condition
Sample code
public class Main {
public static void main(String[] args) {
int i = 4;
do {
System.out.println("hello world");
}while (i<3);
}
}
Printing patterns
4*4 rectangle
import java.util.*;
public class Main {
public static void main(String[] args) {
for (int i =0 ;i<4;i++){
for (int j=0;j<4;j++){
System.out.print("*");
}
System.out.println();
}
}
}
Hollow rectangle
import java.util.*;
public class Main {
public static void main(String[] args) {
int num1=5;
int num2=7;
for (int i=1;i<=num1;i++){
for (int j=1;j<=num2;j++){
if (i==1 || i==num1 || j==1 || j==num2){
System.out.print("*");
JAVA
6
}else{
System.out.print(" ");
}
}
System.out.println();
}
}
}
Different patterns
import java.util.*;
public class Main {
public static void main(String[] args) {
for (int i=0;i<4;i++){
for (int j=0;j<=i;j++){
System.out.print("*");
}
System.out.println();
}
}
}
import java.util.*;
public class Main {
public static void main(String[] args) {
int n=4;
for (int i=n;i>=1;i--){
for (int j=0;j<i;j++){
System.out.print("*");
}
System.out.println();
}
}
}
0-1 Triangle
import java.util.*;
public class Main {
public static void main(String[] args) {
JAVA
7
int n=4;
for (int i=0;i<=n;i++){
for (int j=0;j<=i;j++){
if ((i+j)%2==0){
System.out.print(1);
}else{
System.out.print(0);
}
}
System.out.println();
}
}
}
Functions
Syntax
public static returnType functionName (type arg1,type arg2,...){
operations;
}
Example (sum of two number using functions)
class SumOfTwo {
public static int sumOfTwo(int num1,int num2){
return num1+num2;
}
public static void main(String[] args) {
int num1=4;
int num2=5;
System.out.print(sumOfTwo(num1,num2));
}
}
Factorial using function
import java.util.*;
public class functions {
public static int factorial(int num){
JAVA
8
int fact=1;
for (int i = 1;i<=num;i++){
fact=fact*i;
}
return fact;
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int num=5;
System.out.print(factorial(num));
}
}
Factorial using recursion
import java.util.*;
public class functions {
public static int factorial(int num){
if (num<1){
return 1;
}else {
return num*factorial(num-1);
}
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int num=5;
System.out.print(factorial(num));
}
}
Array
1D array
Defining
type[] arrName = new type[size];
Pre-Defined array
type[] arrName = {1,2,3,4,5};
Basic 1D array code
JAVA
9
import java.util.*;
public class Array {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int[] arr = new int[5];//you can take arr size from user as well
for (int i=0;i<arr.length;i++){
arr[i]=sc.nextInt();
}
for (int i=0;i<arr.length;i++){
System.out.println(arr[i]);
}
}
}
2D array
Declaration
type[][] arrName = new type[size][size];
Sample code
import java.util.*;
public class Array {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int[][] arr = new int[3][3];
for (int i=0;i<3;i++){
for (int j=0;j<3;j++){
arr[i][j]=sc.nextInt();
}
}
for (int i=0;i<3;i++){
for (int j=0;j<3;j++){
System.out.print(arr[i][j]);
}
System.out.println();
}
}
}
Strings
Taking input
JAVA
10
import java.util.*;
public class Strings {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String name = sc.next();//here it will only take first word as an input
System.out.print(name);
}
}
Many words as an input
import java.util.*;
public class Strings {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String name = sc.nextLine();
System.out.print(name);
}
}
Concatenation of strings
public class Strings {
public static void main(String[] args) {
String fName="Vaibhav";
String lName="Patel";
System.out.print(fName+" "+lName);
}
}
Length of string
public class Strings {
public static void main(String[] args) {
String firstName="Vaibhav";
System.out.print(firstName.length());
}
}
JAVA
11
charAt in string
public class Strings {
public static void main(String[] args) {
String firstName="java";
for (int i = 0;i<firstName.length();i++){
System.out.println(firstName.charAt(i));
}
}
}
comparison of strings
it compares first letter of two strings and which ever is greater it
will return accordingly also if the letter is equal then it will move
to next letter
public class Strings {
public static void main(String[] args) {
String first="java";
String second="aava";
//first > second = +ve value
//first == second = 0
//first < second = -ve value
if (first.compareTo(second)==0){
System.out.print("strings are equal");
}else{
System.out.print("strings are not equal");
}
}
}
JAVA
12