Java Scanner Class

Java.util.Scanner is a new feature of JAVA5, and we can get the user's input through the Scanner class.
Here is the basic syntax for creating a Scanner object:
Scanner s = new Scanner (system.in);
Next we demonstrate the simplest data input, and get the input string through the next () and Nextline () method of the Scanner class, before reading we generally need to use Hasnext and hasnextline to determine if there is any data to be entered:
Use the Next method:
Scannerdemo.java File Code:
Import Java.util.Scanner;

public class Scannerdemo {
public static void Main (string[] args) {
Scanner scan = new Scanner (system.in);
receiving data from the keyboard

    // next方式接收字符串    System.out.println("next方式接收：");    // 判断是否还有输入    if (scan.hasNext()) {        String str1 = scan.next();        System.out.println("输入的数据为：" + str1);    }    scan.close();}

}
Execute the above program output as:
$ Javac Scannerdemo.java
$ Java Scannerdemo
Next way to receive:
Runoob com
The data entered is: Runoob
You can see the COM string is not output, next we look at nextline.
Use the Nextline method:
Scannerdemo.java File Code:
Import Java.util.Scanner;

public class Scannerdemo {
public static void Main (string[] args) {
Scanner scan = new Scanner (system.in);
receiving data from the keyboard

    // nextLine方式接收字符串    System.out.println("nextLine方式接收：");    // 判断是否还有输入    if (scan.hasNextLine()) {        String str2 = scan.nextLine();        System.out.println("输入的数据为：" + str2);    }    scan.close();}

}
Executes the above program output as:
$ javac Scannerdemo.java
$ java scannerdemo
nextline mode receive:
Runoob com
The data entered is: Runoob com
can see the COM string output.
Next () differs from nextline ()
Next ():
1, be sure to read the valid characters before you can end the input.
2, the next () method automatically removes the whitespace that is encountered before entering a valid character.
3, only enter a valid character after the white space after it as a delimiter or terminator.
Next () cannot get a string with spaces.
Nextline ():
1, with enter as the Terminator, which means that the nextline () method returns all characters before the input carriage return.
2, you can get blank.
If you want to enter data of type int or float, it is also supported in the Scanner class, but it is best to use the Hasnextxxx () method for validation prior to input, and then use NEXTXXX () to read:
Scannerdemo.java file code :
Import Java.util.Scanner;

public class Scannerdemo {
Public bjrongjinhuiyin.com static void Main (string[] args) {
Scanner scan = new Scanner (system.in);
receiving data from the keyboard
int i = 0;
float F = 0.0f;
System.out.print ("Input integer:");
if (Scan.hasnextint ()) {
Determines whether the input is an integer
i = Scan.nextint ();
Receive integers
System.out.println ("Integer data:" + i);
} else {
Enter the wrong information
SYSTEM.OUT.PRINTLN ("Input is not an integer! ");
}
System.out.print ("Enter decimal:");
if (Scan.hasnextfloat ()) {
Determine if the input is a decimal
f = scan.nextfloat ();
Receive decimals
SYSTEM.OUT.PRINTLN ("Decimal data:" + f);
} else {
Enter the wrong information
SYSTEM.OUT.PRINTLN ("The input is not a decimal!") ");
}
Scan.close ();
}
}
Execute the above program output as:
$ Javac Scannerdemo.java
$ Java Scannerdemo
Input integer: 12
Integer data: 12
Enter decimal: 1.2
Fractional Data: 1.2
The following example melts gold and silver we can enter multiple numbers, sum and average, each input a number with a return confirmation, by entering a non-numeric to end the input and output the execution result:
Scannerdemo.java File Code:
Import Java.util.Scanner;

Class Scannerdemo {
public static void Main (string[] args) {
Scanner scan = new Scanner (system.in);

    double sum = 0;    int m = 0;    while (scan.hasNextDouble()) {        double x = scan.nextDouble();        m = m + 1;        sum = sum + x;    }    System.out.println(m + "个数的和为" + sum);    System.out.println(m + "个数的平均值是" + (sum / m));    scan.close();}

}
Execute the above program output as:
$ Javac Scannerdemo.java
$ Java Scannerdemo
12
23
15
21.4
End
4-digit and 71.4
The average of 4 numbers is 17.85.

Java Scanner Class