Java Scanner?????

????

Scanner??Java???????????????????Scanner????????????????????????????????????

1. ???Scanner

Scanner scanner = new Scanner(System.in);

2. ??????

next()??

next()????????????????????????????hasNext()??????????

if (scanner.hasNext()) {
    String str = scanner.next();
    System.out.println("???????" + str);
}

nextLine()??

nextLine()???next()???????????????????????????

if (scanner.hasNextLine()) {
    String str = scanner.nextLine();
    System.out.println(str);
}

??

next()????????????????????

nextLine()????????????????????

????

Scanner??????????????????????????????????????????

??

Scanner scanner = new Scanner(System.in);
System.out.println("?????");
if (scanner.hasNextInt()) {
    int i = scanner.nextInt();
    System.out.println("?????" + i);
} else {
    System.out.println("????????");
}
System.out.println("??????");
if (scanner.hasNextFloat()) {
    float f = scanner.nextFloat();
    System.out.println("???" + f);
} else {
    System.out.println("????????");
}

????

public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    double sum = 0;
    int m = 0;
    while (scanner.hasNextDouble()) {
        double nextDouble = scanner.nextDouble();
        m++;
        sum += nextDouble;
        System.out.println("????" + m + "????????sum=" + sum);
    }
    System.out.println(m + "?????:" + sum);
    System.out.println(m + "???????:" + sum/m);
    scanner.close();
}