java hasnext
扫描器类的hasNext()方法 (Scanner Class hasNext() method)
Syntax:
句法：
public boolean hasNext();
public boolean hasNext(Pattern patt);
public boolean hasNext(String patt);
hasNext() method is available in java.util package.
hasNext()方法在java.util包中可用。
hasNext() method is used to check whether this Scanner has any other token exists in its input or not.
hasNext()方法用于检查此扫描程序的输入中是否存在其他令牌。
hasNext(Pattern patt) method is used to check whether the next complete token meets the given pattern or not.
hasNext(Pattern patt)方法用于检查下一个完整令牌是否满足给定模式。
hasNext(String patt) method is used to check whether the next complete token meets the pattern (patt) formed from the given string.
hasNext(String patt)方法用于检查下一个完整令牌是否满足从给定字符串形成的模式(patt)。
These methods may throw an exception at the time of checking the given pattern.
这些方法在检查给定模式时可能会引发异常。
IllegalStateException: This exception may throw when this Scanner is not opened.
IllegalStateException ：如果未打开此扫描器，则可能引发此异常。
These are non-static methods, it is accessible with class object & if we try to access these methods with the class name then we will get an error.
这些是非静态方法，可通过类对象访问；如果尝试使用类名称访问这些方法，则会收到错误消息。
Parameter(s):
参数：
In the first case, hasNext(),
在第一种情况下， hasNext() ，
- It does not accept any parameter.
In the second case, hasNext(Pattern patt),
在第二种情况下， hasNext(Pattern patt) ，
- Pattern patt – represents the pattern to read.
- 模式patt –表示要读取的模式。
In the second case, hasNext(String patt),
在第二种情况下， hasNext(String patt) ，
- String patt – represents this string to denotes the pattern to read.
- 字符串patt –表示此字符串，表示要读取的模式。
Return value:
返回值：
In all the cases, the return type of the method is boolean,
在所有情况下，方法的返回类型均为boolean 。
In the first case, it returns true when this Scanner has any other token in its input exists otherwise it returns false.
在第一种情况下，当此扫描程序的输入中存在任何其他令牌时，它返回true ，否则返回false 。
In the second and third case, it returns true when this Scanner has any other token exists meet the given pattern (patt).
在第二种和第三种情况下，当此扫描器具有满足给定模式( patt )的任何其他令牌时，它将返回true 。
Example:
例：
// Java program is to demonstrate the example
// of hasNext() method of Scanner
import java.util.*;
import java.util.regex.*;
public class HasNext {
public static void main(String[] args) {
String str = "Java Programming! 3 * 8= 24";
// Instantiates Scanner
Scanner sc = new Scanner(str);
// By using hasNext() method is to
// check whether this object has more
// token or not
boolean status = sc.hasNext();
System.out.println("sc.hasNext(): " + status);
// By using hasNext(Pattern) method is to
// check whether the given pattern exists
// in this object or not
status = sc.hasNext(Pattern.compile("...a"));
System.out.println("sc.hasNext(Pattern.compile(...a)): " + status);
// By using hasNext(String) method is to
// check whether the given pattern exists
// formed from the given string or not
status = sc.hasNext("..0.a");
System.out.println("sc.hasNext(..0.a): " + status);
// Scanner closed
sc.close();
}
}
Output
输出量
sc.hasNext(): true
sc.hasNext(Pattern.compile(...a)): true
sc.hasNext(..0.a): false
翻译自: https://www.includehelp.com/java/scanner-hasnext-method-with-example.aspx
java hasnext