Java/Development Class/Scanner

Count all vowels inputed from keyboard

   <source lang="java">

import java.util.Scanner; public class CountVowels {

 static Scanner sc = new Scanner(System.in);
 public static void main(String[] args) {
   System.out.print("Enter a string: ");
   String s = sc.nextLine();
   int vowelCount = 0;
   for (int i = 0; i < s.length(); i++) {
     char c = s.charAt(i);
     if ((c == "A") || (c == "a") || (c == "E") || (c == "e") || (c == "I") || (c == "i")
         || (c == "O") || (c == "o") || (c == "U") || (c == "u"))
       vowelCount++;
   }
   System.out.println("That string contains " + vowelCount + " vowels.");
 }

}

</source>
   
  
 
  

Demonstrate findInLine()

   <source lang="java">

/**

*Output:

28

*/

import java.util.Scanner; public class MainClass {

 public static void main(String args[]) {
   String instr = "Name: Joe Age: 28 ID: 77";
   Scanner conin = new Scanner(instr);
   conin.findInLine("Age:"); // find Age
   if (conin.hasNext())
     System.out.println(conin.next());
   else
     System.out.println("Error!");
 }

}

      </source>
   
  
 
  

Letting the user decide when to quit

   <source lang="java">

import java.util.Scanner; public class MainClass {

 static Scanner sc = new Scanner(System.in);
 public static void main(String[] args) {
   int number = 2;
   String input;
   while (true) {
     System.out.println(number + " ");
     System.out.print("Do you want to keep counting?" + " (Y or N)");
     input = sc.next();
     if (input.equalsIgnoreCase("N"))
       break;
     number += 2;
   }
 }

}

</source>
   
  
 
  

Read int by using Scanner Class

   <source lang="java">

import java.util.Scanner; public class MainClass {

 static Scanner sc = new Scanner(System.in);
 public static void main(String[] args) {
   System.out.print("Enter an integer: ");
   int x = sc.nextInt();
   System.out.println("You entered " + x + ".");
 }

}

</source>
   
  
 
  

Test the input string in the while condition.

   <source lang="java">

import java.util.Scanner; public class MainClass {

 static Scanner sc = new Scanner(System.in);
 public static void main(String[] args) {
   int number = 2;
   String input = "Y";
   while (input.equalsIgnoreCase("Y")) {
     System.out.println(number + " ");
     System.out.print("Do you want to keep counting?" + " (Y or N)");
     input = sc.next();
     number += 2;
   }
 }

}

</source>
   
  
 
  

Use Scanner to compute an average a list of comma-separated values

   <source lang="java">

/**

*Output:
Average is 6.2
*/

import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.util.Scanner; public class MainClass {

 public static void main(String args[]) throws IOException {
   int count = 0;
   double sum = 0.0;
   FileWriter fout = new FileWriter("test.txt");
   fout.write("2, 3.4,    5,6, 7.4, 9.1, 10.5, done");
   fout.close();
   FileReader fin = new FileReader("Test.txt");
   Scanner src = new Scanner(fin);
   src.useDelimiter(", *");
   while (src.hasNext()) {
     if (src.hasNextDouble()) {
       sum += src.nextDouble();
       count++;
     } else {
       String str = src.next();
       if (str.equals("done"))
         break;
       else {
         System.out.println("File format error.");
         return;
       }
     }
   }
   fin.close();
   System.out.println("Average is " + sum / count);
 }

}

      </source>
   
  
 
  

Use Scanner to compute an average of the values

   <source lang="java">

/**

*Output:
*/

import java.util.Scanner; public class MainClass {

 public static void main(String args[]) {
   Scanner conin = new Scanner(System.in);
   int count = 0;
   double sum = 0.0;
   System.out.println("Enter numbers to average.");
   while (conin.hasNext()) {
     if (conin.hasNextDouble()) {
       sum += conin.nextDouble();
       count++;
     } else {
       String str = conin.next();
       if (str.equals("done"))
         break;
       else {
         System.out.println("Data format error.");
         return;
       }
     }
   }
   System.out.println("Average is " + sum / count);
 }

}

      </source>
   
  
 
  

Use Scanner to compute an average of the values in a file

   <source lang="java">

/**

*Output:

Average is 6.2

*/

import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.util.Scanner; public class MainClass {

 public static void main(String args[]) throws IOException {
   int count = 0;
   double sum = 0.0;
   FileWriter fout = new FileWriter("test.txt");
   fout.write("2 3.4 5 6 7.4 9.1 10.5 done");
   fout.close();
   FileReader fin = new FileReader("Test.txt");
   Scanner src = new Scanner(fin);
   while (src.hasNext()) {
     if (src.hasNextDouble()) {
       sum += src.nextDouble();
       count++;
     } else {
       String str = src.next();
       if (str.equals("done"))
         break;
       else {
         System.out.println("File format error.");
         return;
       }
     }
   }
   fin.close();
   System.out.println("Average is " + sum / count);
 }

}

      </source>
   
  
 
  

use Scanner to read input that contains several different types of data

   <source lang="java">

import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.util.Scanner; class ScanMixed {

 public static void main(String args[]) throws IOException {
   int i;
   double d;
   boolean b;
   String str;
   FileWriter fout = new FileWriter("test.txt");
   fout.write("Testing Scanner 10 12.2 one true two false");
   fout.close();
   FileReader fin = new FileReader("Test.txt");
   Scanner src = new Scanner(fin);
   while (src.hasNext()) {
     if (src.hasNextInt()) {
       i = src.nextInt();
       System.out.println("int: " + i);
     } else if (src.hasNextDouble()) {
       d = src.nextDouble();
       System.out.println("double: " + d);
     } else if (src.hasNextBoolean()) {
       b = src.nextBoolean();
       System.out.println("boolean: " + b);
     } else {
       str = src.next();
       System.out.println("String: " + str);
     }
   }
   fin.close();
 }

}

</source>
   
  
 
  

Use Scanner to read user input

   <source lang="java">

import java.util.Scanner; class Console {

 static Scanner sc = new Scanner(System.in);
 public static boolean askYorN(String prompt) {
   while (true) {
     String answer;
     System.out.print("\n" + prompt + " (Y or N) ");
     answer = sc.next();
     if (answer.equalsIgnoreCase("Y"))
       return true;
     else if (answer.equalsIgnoreCase("N"))
       return false;
   }
 }

} public class MainClass {

 public static void main(String[] args) {
   while (Console.askYorN("Keep going?")) {
     System.out.println("!");
   }
 }

}

</source>
   
  
 
  

Use Scanner to read various types of data from a file

   <source lang="java">

/**

*Output:

String: Testing String: Scanner int: 10 double: 12.2 String: one boolean: true String: two boolean: false

*/

import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.util.Scanner; public class MainClass {

 public static void main(String args[]) throws IOException {
   int i;
   double d;
   boolean b;
   String str;
   FileWriter fout = new FileWriter("test.txt");
   fout.write("Testing Scanner 10 12.2 one true two false");
   fout.close();
   FileReader fin = new FileReader("Test.txt");
   Scanner src = new Scanner(fin);
   while (src.hasNext()) {
     if (src.hasNextInt()) {
       i = src.nextInt();
       System.out.println("int: " + i);
     } else if (src.hasNextDouble()) {
       d = src.nextDouble();
       System.out.println("double: " + d);
     } else if (src.hasNextBoolean()) {
       b = src.nextBoolean();
       System.out.println("boolean: " + b);
     } else {
       str = src.next();
       System.out.println("String: " + str);
     }
   }
   fin.close();
 }

}

      </source>