????java.util.Scanner ?? Java5 ???????????????????? Scanner ????????????????
????????????? Scanner ????????????
????Scanner s = new Scanner(System.in);
?????????????????????????????????????? Scanner ??? next() ?? nextLine() ?????????????????????????????????? ??? hasNext ?? hasNextLine ?ж????????????????
??????? next ?????? ScannerDemo.java ??????? import java.util.Scanner; public class ScannerDemo { public static void main(String[] args) { Scanner scan = new Scanner(System.in); // ???????????? //next???????????? System.out.println("next????????"); // ?ж?????????? if(scan.hasNext()){ String str1 = scan.next(); System.out.println("????????????"+str1); } } }
???????????????????????
????$ javac ScannerDemo.java
????$ java ScannerDemo
????next????????
????runoob com
????????????????runoob
??????????? com ???????δ???????????????? nextLine??
??????? nextLine ?????? ScannerDemo.java ??????? import java.util.Scanner; public class ScannerDemo { public static void main(String[] args) { Scanner scan = new Scanner(System.in); // ???????????? //nextLine???????????? System.out.println("nextLine????????"); // ?ж?????????? if(scan.hasNextLine()){ String str2 = scan.nextLine(); System.out.println("????????????"+str2); } } }
???????????????????????
????$ javac ScannerDemo.java
????$ java ScannerDemo
????nextLine????????
????runoob com
????????????????runoob com
??????????? com ??????????
????next() ?? nextLine() ????
????next():
????1?????????????Ч???????????????? 2??????????Ч??????????????next() ????????????????? 3???????????Ч????????????????????????????????????? next() ?????????п??????????
????nextLine()??
????1????Enter????????????? nextLine()?????????????????????????????? 2???????????
???????????? int ?? float ???????????? Scanner ?????????????????????????????? hasNextXxx() ?????????????????? nextXxx() ???????
????ScannerDemo.java ??????? import java.util.Scanner; public class ScannerDemo { public static void main(String[] args) { Scanner scan = new Scanner(System.in); // ???????????? int i = 0 ; float f = 0.0f ; System.out.print("??????????"); if(scan.hasNextInt()){ // ?ж??????????????? i = scan.nextInt() ; // ???????? System.out.println("?????????" + i) ; }else{ // ??????????? System.out.println("??????????????") ; } System.out.print("????С????"); if(scan.hasNextFloat()){ // ?ж???????????С?? f = scan.nextFloat() ; // ????С?? System.out.println("С???????" + f) ; }else{ // ??????????? System.out.println("????????С????") ; } } }
???????????????????????
????$ javac ScannerDemo.java
????$ java ScannerDemo
??????????????12
?????????????12
????????С????1.2
????С???????1.2
??????????????????????????????????????????????????????????????????????????????????????????????н????
????ScannerDemo.java ??????? 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+"????????"+sum); System.out.println(m+"????????????"+(sum/m)); } }
???????????????????????
????$ javac ScannerDemo.java
????$ java ScannerDemo
????12
????23
????15
????21.4
????end
????4????????71.4
????4????????????17.85