JAVA语言编程中如何使用表达式

JAVA语言编程中如何使用表达式

JAVA 正则表达式涉及的三个类:

String,Pattern,Matcher

Pattern是要匹配的模式,Matcher是匹配的结果.

例如:Pattern p = Pattern.complie("[a-z]{3}");

Matcher m = p.mather("abc");

要想在正则表达式中匹配一个反斜线用四个反斜线表示: "\\".matches("\\\\");

匹配空白行 " \n".matches("^[\\s&&[^\\n]]*\\n$");

找出匹配结果在整个字符串的开始位置和结束位置

Pattern p = Pattern.complie("\\d{3,5}");

String a = "123-2135-155-00";

Matcher m = p.matcher(s);

m.matches() // 匹配整个字符串,所以这里是false;

m.reset();

while(m.find()) // 找一个和这个模式所匹配的子串

{

System.out.println(m.start() + "To" + m.end());

}

将匹配到的java都转换成大写的

Pattern p = Pattern.complie("java", Pattern.CASE_INSENSITIVE);

Matcher m = p.matcher("java Java JaVa IloveJava You HateJaVA");

m.replaceAll("JAVA");

将匹配偶数个转换为大写,奇数个转换为小写

package zx.test;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

public class TestPattern

{

public static void main(String[] args)

{

StringBuffer newString = new StringBuffer();

String isPatternString = "java Java JaVa IloveJava You HateJaVA";

Pattern p = Pattern.compile("java", Pattern.CASE_INSENSITIVE);

Matcher m = p.matcher(isPatternString);

int i = 0;

while(m.find())

{

i++;

if (i % 2 == 0)

{

m.appendReplacement(newString, "java");

}

else

{

m.appendReplacement(newString, "JAVA");

}

}

m.appendTail(newString);

System.out.println(newString);

}

}

输出结果:JAVA java JAVA Ilovejava You HateJAVA

Java正则表达式分组:

private static void testGroup()

{

String s = "3412afdsaf-34ijii-422342k23-423423fsdfaf";

Pattern p = Pattern.compile("(\\d{1,10})([a-z]{1,9})"); // 组1:(\\d{1,10}) 组2:([a-z]{1,9})

Matcher m = p.matcher(s);

while(m.find())

{

System.out.println("Group0: " + m.group() + " Group1: " + m.group(1) + " Group2: " + m.group(2));

}

}

输出结果:

Group0: 3412afdsaf Group1: 3412 Group2: afdsaf

Group0: 34ijii Group1: 34 Group2: ijii

Group0: 422342k Group1: 422342 Group2: k

Group0: 423423fsdfaf Group1: 423423 Group2: fsdfaf