java.util.Scanner类的nextBoolean()方法将输入的下一个标记扫描为布尔值。如果翻译成功,则扫描程序将前进经过匹配的输入。
用法:
public boolean nextBoolean()
参数:该函数不接受任何参数。
返回值:此函数返回从输入扫描的布尔值。
异常:该函数引发三个异常,如下所述:
- InputMismatchException:如果下一个标记不是有效的布尔值
- NoSuchElementException:如果输入已用尽则抛出
- IllegalStateException:如果此扫描仪关闭,则抛出
以下示例程序旨在说明上述函数:
示例1:
// Java program to illustrate the
// nextBoolean() 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 true 9 + 6 = 12.0 false";
// create a new scanner
// with the specified String Object
Scanner scanner = new Scanner(s);
while (scanner.hasNext()) {
// if the next is a Boolean,
// print found and the Boolean
if (scanner.hasNextBoolean()) {
System.out.println("Found Boolean value :"
+ scanner.nextBoolean());
}
// if no Boolean is foucnd,
// print "Not Found:" and the token
else {
System.out.println("Not found Boolean() value :"
+ scanner.next());
}
}
scanner.close();
}
}
输出:
Not found Boolean() value :Gfg Found Boolean value :true Not found Boolean() value :9 Not found Boolean() value :+ Not found Boolean() value :6 Not found Boolean() value := Not found Boolean() value :12.0 Found Boolean value :false
示例2:演示InputMismatchException
// Java program to illustrate the
// nextBoolean() 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 Boolean
// print found and the Boolean
// since the value 60 is out of range
// it throws an exception
System.out.println("Next Boolean value :"
+ scanner.nextBoolean());
}
scanner.close();
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
输出:
Exception thrown: java.util.InputMismatchException
示例3:演示NoSuchElementException
// Java program to illustrate the
// nextBoolean() 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 Boolean value
// more times than the scanner
// Hence it will throw exception
for (int i = 0; i < 5; i++) {
// if the next is a Boolean,
// print found and the Boolean
if (scanner.hasNextBoolean()) {
System.out.println("Found Boolean value :"
+ scanner.nextBoolean());
}
// if no Boolean is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Boolean value :"
+ scanner.next());
}
}
scanner.close();
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
输出:
Not found Boolean value :Gfg Exception thrown: java.util.NoSuchElementException
示例4:演示IllegalStateException
// Java program to illustrate the
// nextBoolean() 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 Boolean value");
while (scanner.hasNext()) {
// if the next is a Boolean,
// print found and the Boolean
if (scanner.hasNextBoolean()) {
System.out.println("Found Boolean value :"
+ scanner.nextBoolean());
}
// if no Boolean is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Boolean value :"
+ scanner.next());
}
}
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
输出:
Scanner Closed Trying to get next Boolean value Exception thrown: java.lang.IllegalStateException: Scanner closed
参考: https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#nextBoolean()
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