Java 中 Scanner nextFloat()方法，带示例
原文:https://www . geesforgeks . org/scanner-next float-method-in-Java-with-examples/
类的 nextFloat() 方法将输入的下一个标记作为 Float()进行扫描。如果翻译成功，扫描仪将通过匹配的输入。
语法:
public float nextFloat()
参数:函数不接受任何参数。
返回值:该功能从输入返回扫描的浮点数。
异常:如果下一个标记与 Float 正则表达式不匹配，或者超出范围
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以下程序说明了上述功能:
程序 1:
// Java program to illustrate the
// nextFloat() 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 Float,
// print found and the Float
if (scanner.hasNextFloat()) {
System.out.println("Found Float value :"
+ scanner.nextFloat());
}
// if no float is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Float() value :"
+ scanner.next());
}
}
scanner.close();
}
}
输出:
Not found Float() value :Gfg
Found Float value :9.0
Not found Float() value :+
Found Float value :6.0
Not found Float() value :=
Found Float value :12.0
程序 2: 演示输入 ismatcheexception
// Java program to illustrate the
// nextFloat() 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 Float
// print found and the Float
// since the value 60 is out of range
// it throws an exception
System.out.println("Next Float value :"
+ scanner.nextFloat());
}
scanner.close();
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
输出:
Exception thrown: java.util.InputMismatchException
程序 3: 演示 nosucheelementexception
// Java program to illustrate the
// nextFloat() 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 Float value
// more times than the scanner
// Hence it will throw exception
for (int i = 0; i < 5; i++) {
// if the next is a Float,
// print found and the Float
if (scanner.hasNextFloat()) {
System.out.println("Found Float value :"
+ scanner.nextFloat());
}
// if no Float is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Float value :"
+ scanner.next());
}
}
scanner.close();
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
输出:
Not found Float value :Gfg
Exception thrown: java.util.NoSuchElementException
程序 4: 演示非法状态异常
// Java program to illustrate the
// nextFloat() 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 Float value");
while (scanner.hasNext()) {
// if the next is a Float,
// print found and the Float
if (scanner.hasNextFloat()) {
System.out.println("Found Float value :"
+ scanner.nextFloat());
}
// if no Float is found,
// print "Not Found:" and the token
else {
System.out.println("Not found Float value :"
+ scanner.next());
}
}
}
catch (Exception e) {
System.out.println("Exception thrown: " + e);
}
}
}
输出:
Scanner Closed
Trying to get next Float value
Exception thrown: java.lang.IllegalStateException: Scanner closed
参考:https://docs . Oracle . com/javase/7/docs/API/Java/util/scanner . html # nextFloat()
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