Java中的 Scanner nextInt() 方法和示例
Java.util.Scanner类的nextInt(radix)方法将输入的下一个标记扫描为 Int。如果翻译成功，扫描仪会超过匹配的输入。如果未传递参数 radix，则它的行为类似于 nextInt(radix)，其中基数被假定为默认基数。
句法：
public int nextInt()参数：该函数接受一个参数基数，该基数用于将标记解释为一个 Int 值。
返回值：此函数返回从输入扫描的 Int 。
异常：该函数抛出三个异常，如下所述：
- InputMismatchException：如果下一个标记与 Integer 正则表达式不匹配，或者超出范围
- NoSuchElementException：如果输入用尽则抛出
- IllegalStateException：如果此扫描仪关闭则抛出
下面的程序说明了上述函数：
方案一：
// Java program to illustrate the
// nextInt() method of Scanner class in Java
// without parameter
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
String s = "Gfg 9 + 6 = 12.0";
// create a new scanner
// with the specified String Object
Scanner scanner = new Scanner(s);
while (scanner.hasNext()) {
// if the next is a Int,
// print found and the Int
if (scanner.hasNextInt()) {
System.out.println("Found Int value :"
+ scanner.nextInt());
}
// if no Int is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Int value :"
+ scanner.next());
}
}
scanner.close();
}
}
输出：
Not found Int value :Gfg
Found Int value :9
Not found Int value :+
Found Int value :6
Not found Int value :=
Not found Int value :12.0
方案二：
// Java program to illustrate the
// nextInt() method of Scanner class in Java
// with parameter
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
String s = "Gfg 9 + 6 = 12.0";
// create a new scanner
// with the specified String Object
Scanner scanner = new Scanner(s);
while (scanner.hasNext()) {
// if the next is a Int,
// print found and the Int
if (scanner.hasNextInt()) {
System.out.println("Found Int value :"
+ scanner.nextInt(12));
}
// if no Int is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Int value :"
+ scanner.next());
}
}
scanner.close();
}
}
输出：
Not found Int value :Gfg
Found Int value :9
Not found Int value :+
Found Int value :6
Not found Int value :=
Not found Int value :12.0
程序 3：演示 InputMismatchException
// Java program to illustrate the
// nextInt() method of Scanner class in Java
// InputMismatchException
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
try {
String s = "Gfg 9 + 6 = 12.0";
// create a new scanner
// with the specified String Object
Scanner scanner = new Scanner(s);
while (scanner.hasNext()) {
// if the next is a Int,
// print found and the Int
// since the value 60 is out of range
// it throws an exception
System.out.println("Next Int value :"
+ scanner.nextInt());
}
scanner.close();
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
输出：
Exception thrown: java.util.InputMismatchException
程序 4：演示 NoSuchElementException
// Java program to illustrate the
// nextInt() method of Scanner class in Java
// NoSuchElementException
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
try {
String s = "Gfg";
// create a new scanner
// with the specified String Object
Scanner scanner = new Scanner(s);
// Trying to get the next Int value
// more times than the scanner
// Hence it will throw exception
for (int i = 0; i < 5; i++) {
// if the next is a Int,
// print found and the Int
if (scanner.hasNextInt()) {
System.out.println("Found Int value :"
+ scanner.nextInt());
}
// if no Int is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Int value :"
+ scanner.next());
}
}
scanner.close();
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
输出：
Not found Int value :Gfg
Exception thrown: java.util.NoSuchElementException
程序 5：演示 IllegalStateException
// Java program to illustrate the
// nextInt() method of Scanner class in Java
// IllegalStateException
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
try {
String s = "Gfg 9 + 6 = 12.0";
// create a new scanner
// with the specified String Object
Scanner scanner = new Scanner(s);
// close the scanner
scanner.close();
System.out.println("Scanner Closed");
System.out.println("Trying to get "
+ "next Int value");
while (scanner.hasNext()) {
// if the next is a Int,
// print found and the Int
if (scanner.hasNextInt()) {
System.out.println("Found Int value :"
+ scanner.nextInt());
}
// if no Int is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Int value :"
+ scanner.next());
}
}
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
输出：
Scanner Closed
Trying to get next Int value
Exception thrown: java.lang.IllegalStateException: Scanner closed
参考： https: Java/util/Scanner.html#nextInt(int)