30 Days of Java

On Day 2 of 30 days of Java, I learned about Scanner for getting user input.

Java Scanner class:

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);  // Create a Scanner object
    System.out.println("Enter Name");

    String name = scan.nextLine();  // Read user input
    System.out.println("Name is: " + name);  // Output user input

    int age = scan.nextInt();  // Read user input
    System.out.println("Age is: " + age);  // Output user input    

  }
}

Reading user input:

In the above example, nextLine() has been used to read a string input. For other data types:

nextBoolean() Reads a boolean value from the user
nextByte() Reads a byte value from the user
nextDouble() Reads a double value from the user
nextFloat() Reads a float value from the user
nextInt() Reads a int value from the user
nextLine() Reads a String value from the user
nextLong() Reads a long value from the user
nextShort() Reads a short value from the user

nextLine() Trap:

**Trap: Putting nextLine() ahead of nextInt(), nextDouble(), nextLong(), or next().

Solution: add a throwaway nextLine() before the real nextLine() other wise nextLine() will not skip the whitespace (delimiter).

Comparison Operators in Java:

Java Switch Statements

int month = 2;
switch(month) {
  case 1:
    System.out.println("Jan");
    break;
  case 2:
    System.out.println("Feb");
    break;
  default:
    System.out.println("Mar");
}
// Outputs "Feb" (month 2)

Functions in Java

Functions in Java have the following structure:

<access_modifier> <return_type> <method_name>( list_of_parameters)
{
    //body
}

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

    int numberOfPeople = countPeople(12, 15);

    public int countPeople(int group1, int group2){
    int people = group1+group2;
    return people;
    }
  }
}

where

access_modifier can be public, private,...
return_type can be void, int, String,...
method_name can be sth like countPeople,...
parameters' type should be declared (int num1, int num2)

30 Days of Java | Day 2

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