Java Scanner next（）方法与示例

扫描仪类的next()方法 (Scanner Class next() method)

Syntax:

句法：

    public String next();
public String next(Pattern patt);
public String next(String patt);

next() method is available in java.util package.
next()方法在java.util包中可用。
next() method is used to search & get the next complete token from this Scanner and a token is preceded & followed by the input that meets the pattern.
next()方法用于搜索并从此扫描器中获取下一个完整令牌，令牌之前和之后是符合模式的输入。
next(Pattern patt) method is used to retrieve the next token when it meets the given Pattern (patt).
next(Pattern patt)方法用于在遇到给定Pattern(patt)时检索下一个标记。
next(String patt) method is used to retrieve the next token when it meets the pattern formed from the given String (patt).
next(String patt)方法用于在下一个令牌遇到由给定String(patt)形成的模式时检索下一个令牌。
These methods may throw an exception at the time of representing a token as a pattern.
这些方法在将令牌表示为模式时可能会引发异常。
- NoSuchElementException: This exception may throw when no more token exists.NoSuchElementException ：如果不再存在令牌，则可能引发此异常。
- 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, next(),
在第一种情况下， next() ，
- It does not accept any parameter.
In the first case, next(Pattern patt),
在第一种情况下， next(Pattern patt) ，
- Pattern patt – represents the pattern (patt) to read.
- 模式patt –表示要读取的模式(patt)。
In the second case, next(String patt),
在第二种情况下， next(String patt) ，
- String patt – represents the string to define the pattern (patt) to read.
- 字符串patt –表示用于定义要读取的图案(图案)的字符串。

Return value:

返回值：

In all the cases, the return type of the method is String, it retrieves the next token

在所有情况下，方法的返回类型为String ，它检索下一个标记

Example 1:

范例1：

// Java program is to demonstrate the example 
// of next() method of Scanner
import java.util.*;
import java.util.regex.*;
public class Next {
public static void main(String[] args) {
String str = "Java Programming! 3 * 8= 24";
// Instantiates Scanner
Scanner sc = new Scanner(str);
// By using next() method is to
// display the next complete 
// token
String next = sc.next();
System.out.println("sc.next(): " + next);
// Scanner closed
sc.close();
}
}

Output

输出量

sc.next(): Java

Example 2:

范例2：

import java.util.*;
import java.util.regex.*;
public class Next {
public static void main(String[] args) {
String str = "Java Programming! 3 * 8= 24";
// Instantiates Scanner
Scanner sc = new Scanner(str);
// By using net(Pattern) method is
// to return the next token when it meets
// the given pattern
String next_p = sc.next(Pattern.compile("J..a"));
System.out.println("sc.next(Pattern.compile(J..a)): " + next_p);
// Scanner closed
sc.close();
}
}

Output

输出量

sc.next(Pattern.compile(J..a)): Java

Example 3:

范例3：

import java.util.*;
import java.util.regex.*;
public class Next {
public static void main(String[] args) {
String str = "Java Programming! 3 * 8= 24";
// Instantiates Scanner
Scanner sc = new Scanner(str);
// By using net(String) method is
// to return the next token when it meets
// the given pattern formed from the given
// string
String next_s = sc.next("Java");
System.out.println("sc.next(Java)): " + next_s);
// Scanner closed
sc.close();
}
}

Output

输出量