Java 正则表达式元字符示例

正则表达式 定义字符串的搜索模式。对于给定的字符串，此模式可能匹配一次或多次或根本不匹配。正则表达式的缩写是regex。正则表达式可用于搜索、编辑和操作文本。

1. 元字符的Java正则表达式列表

正则表达式支持一些具有明确预定义含义的元字符或特殊字符。以下元字符使某些常见模式更易于使用，例如'd' 而不是 [0..9]。

1. Java正则表达式元字符示例

package com.howtodoinjava.regex;

import junit.framework.Assert;

import org.junit.Test;

public class MetaCharactersTest
{
	@Test
	public void testAnyDigit()
	{
		/**
		 * Matches exactly 3 digits
		 * */
		String sampleText = "123";
		String regex = "d{3}";
		Assert.assertEquals(true, sampleText.matches(regex));
	}

	@Test
	public void testNonDigit()
	{
		/**
		 * Matches exactly 3 non digits
		 * */
		String sampleText = "abc";
		String regex = "d{3}";
		Assert.assertNotSame(true, sampleText.matches(regex));
	}

	@Test
	public void testWhiteSpaceCharacters()
	{
		/**
		 * Matches n number of spaces
		 * */
		String sampleText = "     ";
		String regex = "s{0,}";
		Assert.assertEquals(true, sampleText.matches(regex));
	}

	@Test
	public void testNonWhiteSpaceCharacter1()
	{
		/**
		 * Matches no space allowed
		 * */
		String sampleText = "abc123";
		String regex = "S{0,}";
		Assert.assertEquals(true, sampleText.matches(regex));
	}

	@Test
	public void testNonWhiteSpaceCharacter2()
	{
		/**
		 * Matches no space allowed with '+' sign
		 * */
		String sampleText = "abc123";
		String regex = "S+";
		Assert.assertEquals(true, sampleText.matches(regex));
	}

	@Test
	public void testWordCharacter()
	{
		/**
		 * Matches one or more word characters
		 * */
		String sampleText = "abc123";
		String regex = "w{0,}";
		Assert.assertEquals(true, sampleText.matches(regex));
	}

	@Test
	public void testNonWordCharacter()
	{
		/**
		 * Matches one or more word characters
		 * */
		String sampleText1 = "abc123";
		String sampleText2 = "!@#$";
		String regex = "W{0,}";
		Assert.assertNotSame(true, sampleText1.matches(regex));
		Assert.assertEquals(true, sampleText2.matches(regex));
	}

	@Test
	public void testWordBoundary()
	{
		/**
		 * Matches the word "abc123" exactly same
		 * */
		String sampleText = "abc123";
		String regex = "babc123b";
		Assert.assertEquals(true, sampleText.matches(regex));
	}
}

在这个 Java 正则表达式示例 中，我们学习了在正则表达式中使用元字符来评估文本字符串。

快乐学习！！

标签2： Java Regular Expressions Regular Expressions

地址：https://www.cundage.com/article/regular-expressions-meta-characters.html