Your First Java program

Lesson#1

Like most other programming language tutorials I will start with writing a Java program that prints “Hello World” on the screen. Here it is:

class P001_HelloWorld
{
 public static void main(String args[])
 {…

Data Types in Java

Output:

b=-128, s=-32768, i=2147483647, l=9223372036854775806, 

 f=3.4E38, d=1.7E308

The following statements will give error at compile time:

Escape sequence in Java

class P002_EscapeSequence
{
 public static void main(String args[])
 {
  System.out.println("One\nTwo\rThree\tFour\bFive\fSix");
 }
}

Output:

One
TwoThree FourFiveSix

Data Types in Java

Output:

aint= 10 afloat=7.7777776E7 adouble=7.7777776E7 aboolean=false

Forward Referencing in Java

class P006_ForwardReference
{
 public static void main(String args[])
 {
  A a=new A();
  System.out.println(a.x); // 100
 }
}

class A
{
 //int m=n; illegal forward reference
 int n=30;
 int x=getVal();
 
 int getVal() { return 100; }
}

Java Program to add two numbers

class P003_Addition
{
 public static void main(String args[])
 {
  int No1,No2,Sum;
  No1=10;
  No2=20;
  Sum=No1+No2;
  System.out.println("Sum=" + Sum);
 }
}

Output:

sum=30

Scope of variables in Java

class P005_Scope
{
 public static void main(String args[])
 {
  {
   int i=100;
  }
  
  // line below gives the error: can not resolve symbol i
  System.out.println(i);
 }
}