Java StringTokenizer 类介绍
概述
StringTokenizer 是一个遗留类，用于将字符串分割成标记（tokens）。
但在现代 Java 开发中已被更强大的 String.split() 和 Scanner 类取代，新项目应使用更现代的解决方案。
基本用法
1. 构造方法
// 1. 默认分隔符（空格、制表符、换行符等）
StringTokenizer st1 = new StringTokenizer("Hello World Java");
// 2. 指定分隔符
StringTokenizer st2 = new StringTokenizer("A,B,C", ",");
// 3. 指定分隔符并返回分隔符
StringTokenizer st3 = new StringTokenizer("A,B,C", ",", true);
方法
详细示例
示例1：基本分割
public class BasicExample {
public static void main(String[] args) {
String data = "Java;Python;JavaScript;C++";
StringTokenizer st = new StringTokenizer(data, ";");
System.out.println("Token数量: " + st.countTokens());
while (st.hasMoreTokens()) {
System.out.println("语言: " + st.nextToken());
}
}
}
示例2：CSV解析
public class CSVExample {
public static void main(String[] args) {
String csv = "John,25,Developer,New York";
StringTokenizer st = new StringTokenizer(csv, ",");
System.out.println("姓名: " + st.nextToken());
System.out.println("年龄: " + st.nextToken());
System.out.println("职业: " + st.nextToken());
System.out.println("城市: " + st.nextToken());
}
}
示例3：复杂分隔符
public class ComplexDelimiter {
public static void main(String[] args) {
String text = "Apple and Banana or Cherry but not Date";
StringTokenizer st = new StringTokenizer(text, " andorbutnot");
while (st.hasMoreTokens()) {
System.out.println(st.nextToken());
}
// 输出: Apple, Banana, Cherry, Date
}
}
现代替代方案
使用 String.split()（推荐）
public class SplitAlternative {
public static void main(String[] args) {
String text = "Apple,Banana,Cherry";
// 简单分割
String[] fruits = text.split(",");
for (String fruit : fruits) {
System.out.println(fruit);
}
// 正则表达式分割
String complexText = "A1,B2,C3";
String[] items = complexText.split(",\\d");
for (String item : items) {
System.out.println(item);
}
}
}
使用 Scanner 类
import java.util.Scanner;
public class ScannerAlternative {
public static void main(String[] args) {
String text = "Apple Banana Cherry";
Scanner scanner = new Scanner(text);
while (scanner.hasNext()) {
System.out.println(scanner.next());
}
scanner.close();
}
}
优缺点
优点
缺点
使用建议
不建议在新项目中使用 StringTokenizer，推荐替代方案：
// 1. 简单分割 - 使用 String.split()
String[] parts = text.split(",");
// 2. 复杂分割 - 使用 Pattern/Matcher
Pattern pattern = Pattern.compile("\\s+");
String[] words = pattern.split(text);
// 3. 流式处理 - 使用 Java 8 Stream
Arrays.stream(text.split(","))
.map(String::trim)
.filter(s -> !s.isEmpty())
.forEach(System.out::println);
Java Scanner 类详解
概述
Scanner 是一个强大的文本扫描器，可以解析原始类型和字符串使用正则表达式。它提供了多种输入解析功能。
基本用法
1. 创建 Scanner 对象
import java.util.Scanner;
public class ScannerBasic {
public static void main(String[] args) {
// 从标准输入创建
Scanner scanner = new Scanner(System.in);
// 从字符串创建
Scanner stringScanner = new Scanner("Hello 123 45.67 true");
// 从文件创建
Scanner fileScanner = new Scanner(new File("data.txt"));
}
}
核心方法
读取不同类型数据
public class ScannerTypes {
public static void main(String[] args) {
Scanner sc = new Scanner("John 25 75000.50 true");
// 读取不同类型
String name = sc.next(); // John
int age = sc.nextInt(); // 25
double salary = sc.nextDouble(); // 75000.50
boolean active = sc.nextBoolean(); // true
System.out.printf("姓名: %s, 年龄: %d, 薪资: %.2f, 状态: %b%n",
name, age, salary, active);
}
}
用户输入示例
import java.util.Scanner;
public class UserInputExample {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("请输入姓名: ");
String name = scanner.nextLine();
System.out.print("请输入年龄: ");
int age = scanner.nextInt();
System.out.print("请输入薪资: ");
double salary = scanner.nextDouble();
// 清除缓冲区
scanner.nextLine();
System.out.print("请输入城市: ");
String city = scanner.nextLine();
System.out.printf("员工信息: %s, %d岁, 薪资%.2f, 城市%s%n", name, age, salary, city);
scanner.close();
}
}
常用方法总结
高级功能
1. 分隔符控制
public class DelimiterExample {
public static void main(String[] args) {
String data = "Apple,Banana;Cherry:Date";
Scanner sc = new Scanner(data);
// 设置自定义分隔符（正则表达式）
sc.useDelimiter("[,;:]");
while (sc.hasNext()) {
System.out.println(sc.next().trim());
}
sc.close();
}
}
2. 区域设置
import java.util.Locale;
public class LocaleExample {
public static void main(String[] args) {
String numbers = "1,234.56 7.890,12";
// 使用美国区域设置
Scanner usScanner = new Scanner(numbers);
usScanner.useLocale(Locale.US);
System.out.println("US: " + usScanner.nextDouble()); // 1234.56
// 使用德国区域设置
Scanner deScanner = new Scanner(numbers);
deScanner.useLocale(Locale.GERMANY);
deScanner.next(); // 跳过第一个数字
System.out.println("DE: " + deScanner.nextDouble()); // 7890.12
}
}
3. 模式匹配
import java.util.regex.Pattern;
public class PatternExample {
public static void main(String[] args) {
String text = "年龄:25 薪资:50000 部门:IT";
Scanner sc = new Scanner(text);
// 查找特定模式
Pattern agePattern = Pattern.compile("年龄:(\\d+)");
Pattern salaryPattern = Pattern.compile("薪资:(\\d+)");
while (sc.hasNext()) {
if (sc.hasNext(agePattern)) {
String age = sc.findInLine(agePattern);
System.out.println("找到年龄: " + age);
} else if (sc.hasNext(salaryPattern)) {
String salary = sc.findInLine(salaryPattern);
System.out.println("找到薪资: " + salary);
} else {
sc.next(); // 跳过不匹配的内容
}
}
sc.close();
}
}
实用示例
1. 文件读取
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class FileScannerExample {
public static void main(String[] args) {
try {
Scanner fileScanner = new Scanner(new File("data.txt"));
while (fileScanner.hasNextLine()) {
String line = fileScanner.nextLine();
System.out.println("行内容: " + line);
}
fileScanner.close();
} catch (FileNotFoundException e) {
System.out.println("文件未找到: " + e.getMessage());
}
}
}
2. CSV 解析
public class CSVScanner {
public static void main(String[] args) {
String csvData = "John,Doe,25,Developer\nJane,Smith,30,Manager";
Scanner sc = new Scanner(csvData);
while (sc.hasNextLine()) {
String line = sc.nextLine();
Scanner lineScanner = new Scanner(line);
lineScanner.useDelimiter(",");
String firstName = lineScanner.next();
String lastName = lineScanner.next();
int age = lineScanner.nextInt();
String job = lineScanner.next();
System.out.printf("%s %s, %d岁, %s%n", firstName, lastName, age, job);
lineScanner.close();
}
sc.close();
}
}
最佳实践
1. 资源管理
// 使用 try-with-resources 自动关闭
public class ResourceManagement {
public static void main(String[] args) {
try (Scanner scanner = new Scanner(System.in)) {
System.out.print("请输入内容: ");
String input = scanner.nextLine();
System.out.println("你输入了: " + input);
}
// scanner 自动关闭
}
}
2. 性能考虑
public class PerformanceTips {
public static void main(String[] args) {
// 对于大文件，设置合适的缓冲区
try (Scanner sc = new Scanner(new File("large.txt"))) {
sc.useDelimiter("\\R"); // 行分隔符
while (sc.hasNext()) {
String line = sc.next();
// 处理每一行
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
Scanner 类的优势：
注意事项：
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