CORE JAVA CHEATSHEET Learn JAVA from experts at https://www.edureka.co
Iterative Statements
Java Programming
Java is a high level, general purpose programming
language that produces software for multiple platforms. It
was developed by James Gosling in 1991 and released by
Sun Microsystems in 1996 and is currently owned by
Oracle.
Arrays In Java
User -Defin ed Exceptions
// for loop
for (condition) {expression}
// for each loop
for (int i: someArray) {}
// while loop
while (condition) {expression}
// do while loop
do {expression} while(condition)
Primitive Data Types
Type Size Range
byte 8 -128..127
short 16 -32,768..32,767
int 32 -2,147,483,648.. 2,147,483,647
long 64 9,223,372,036,854,775,808.. 9,223..
float 32 3.4e-0.38.. 3.4e+0.38
double 64 1.7e-308.. 1.7e+308
char 16 Complete Unicode Character Set
Boolean 1 True, False
Java Operators
Type Operators
Arithmetic +, –, *, ? , %
Assignment =, +=, -=, *=, /=, %=, &=, ^=, |=, <<=, >>=, >>>=
Bitwise ^, &, |
Logical &&, ||
Relational <, >, <=, >=,==, !=
Shift <<, >>, >>>
Ternary ? :
Unary ++x, –x, x++, x–, +x, –x, !, ~
{public|private} [static] type name [= expression|value];
Java Variables
{public|private} [static] {type | void} name(arg1, ...,
argN ){statements}
Java Methods
Data Type Conversion
// Widening (byte<short<int<long<float<double)
int i = 10; //int--> long
long l = i; //automatic type conversion
// Narrowing
double d = 10.02;
long l = (long)d; //explicit type casting
// Numeric values to String
String str = String.valueOf(value);
// String to Numeric values
int i= Integer.parseInt(str);
double d = Double.parseDouble(str);
User Input
// Using BufferReader
BufferedReader reader = new BufferedReader(new
InputStreamReader(System.in));
String name = reader.readLine();
// Using Scanner
Scanner in = new Scanner(System.in);
String s = in.nextLine();
int a = in.nextInt();
// Using Console
String name = System.console().readLine();
Basic Java Program
public class Demo
{
public static void main(String[] args)
{
System.out.println("Hello from edureka!");
}
}
Save
Compile
Execute
className.java
javac className
java className
for (i= 1; i <= n; ++i)
{
System.out.print(t1 + " + ");
int sum = t1 + t2; t1 = t2;
t2 = sum;
}
Fibonacci series
k = 2*n - 2;
for(i=0; i<n; i++)
{
for(j=0; j<k; j++){System.out.print(" ");}
k = k - 1;
for(j=0; j<=i; j++ ){System.out.print("* ");}
System.out.println();
}
Pyramid Pattern
Decisive Statements
//if statement
if (condition) {expression}
//if-else statement
if (condition) {expression} else {expression}
//switch statement
switch (var) { case 1: expression; break;
default: expression; break; }
if (n < 2)
{
return false;
}
for (int i=2; i <= n/i; i++)
{
if (n%i == 0) return false;
}
return true;
Prime Number
// Creating String using literal
String str1 = “Welcome”;
// Creating String using new keyword
String str2 = new String(”Edureka”);
str1==str2 //compare the address;
String newStr = str1.equals(str2); //compares the values
String newStr = str1.equalsIgnoreCase() //
newStr = str1.length() //calculates length
newStr = str1.charAt(i) //extract i'th character
newStr = str1.toUpperCase() //returns string in ALL CAPS
newStr = str1.toLowerCase() //returns string in ALL LOWERCASE
newStr = str1.replace(oldVal, newVal) //search and replace
newStr = str1.trim() //trims surrounding whitespace
newStr = str1.contains("value"); //Check for the values
newStr = str1.toCharArray(); //Convert into character array
newStr = str1.IsEmpty(); //Check for empty String
newStr = str1.endsWith(); //Checks if string ends with the given suffix
1 - Dimensional
// Initializing
type[] varName= new type[size];
// Declaring
type[] varName= new type[]{values1, value2,...};
double[] arr = new double[n];
for (int i=0; i<n; i++)
{a[i] = Math.random();}
Array with Random Variables
double max = 0;
for (int i=0; i<arr.length(); i++)
{ if(a[i] > max) max = a[i]; }
Maximum value in an Array
for(int i=0; i<(arr.length())/2; i++)
{ double temp = a[i];
a[i] = a[n-1-i];
a[n-1-i] = temp; }
Reversing an Array
// Initializing
datatype[][] varName = new dataType[row][col];
// Declaring
datatype[][] varName = {{value1, value2....},{value1,
value2....}..};
Multi –Dimensional Arrays
for(i = 0; i < row; i++)
{ for(j = 0; j < column; j++)
{ System.out.print(array[i][j]+" "); }
System.out.println(" ");
}
Transposing A Matrix
for (i = 0; i < row1; i++)
{ for (j =0; j<col2; j++)
{for (k =0; k < row2; k++)
{ sum = sum + first[i][k]*second[k][j]; }
multiply[i][j] =sum;
sum =0; } }
Multiplying two Matrices
Java Strings
int factorial(int n)
{
if (n == 0)
{return 1;}
else
{
return(n * factorial(n-1));
}
}
Factorial of a Number
String Methods
