本文通过重构Java正则表达式代码，实现字符串中单词、数字和标点的有效分解，展示了如何提升代码的可读性和可维护性。
java 正则表达式的使用及代码重构（优雅代码实现）案列
实现功能 将 the first item is a hamer,with a cost of $132.99. 分解成单个的单词，数字，标点。
/**The following program It tokenizes a string into its
* textual components: words, numbers,
* or punctuation. Although it is a simple example, it illustrates
* the basic techniques used to tokenize any type of input.
*/
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* @author chenhao
*
*/
/**
* @author chenhao
*
*/
public final class SimpleTextTokenizer {
/**
*
*/
private SimpleTextTokenizer() { }
/**
*"\G"表示前一匹配的结尾 ， "/z"表示字符串的结尾（包括）行终止符 end 用来匹配字符串的结尾.
*/
private static Pattern end = Pattern.compile("//G//z");
/**
* "\g\w+" 表示从前一批匹配的结尾开始匹配一个或多个可以成为单词的的.
* 一部分的字符. 如A - Z a-z 0 - 9 及下划线 （单词字符)
*/
private static Pattern wrod = Pattern.compile("\\G\\w+");
/**
* . "/p{Punct}" 包含所有的标点符号
*/
private static Pattern punct = Pattern.compile("\\G\\p{Punct}");
/**
*"\s" 匹配空格.
*/
private static Pattern space = Pattern.compile("\\G\\s");
/**
* . 匹配数字
*/
private static Pattern number = Pattern.compile("\\G\\d+\\.?\\d*");
/**
* the method returns the next token
* retrieved from the Matcher passed to.
* @param mat
* the Matcher of the text
* @return the next token of the text
*/
static String getTextToken(final Matcher mat) {
// First skip leading spaces
mat.usePattern(space);
mat.find();
// Next, obtain the next token in the string
// by attempting to match each pattern.
// The token found by the first matching pattern
// is returned. The order in which the patterns
// are tried matters. Checking for a word
// before checking for a number can change the results.
// First check for a number
mat.usePattern(number);
if (mat.find()) {
return mat.group();
}
// if not a number check for word
mat.usePattern(wrod);
if (mat.find()) {
return mat.group();
}
// check for punction
mat.usePattern(punct);
if (mat.find()) {
return mat.group();
}
// finall check for end of string
mat.usePattern(end);
if (mat.find()) {
return "";
}
// token is not recognized
return null; // invalid token
}
/**
* @param args
*/
public static void main(final String[] args) {
String token;
// Create a matcher
Matcher mat = end.matcher("the first item is a hamer,"
+ "with a cost of $132.99");
// display the tokens in the string
do {
token = getTextToken(mat);
if (token == null) {
System.out.println("invalid token");
break;
}
if (token.length() != 0) {
System.out.println("Token " + token);
} else {
System.out.println("End of String");
}
} while (token.length() != 0);
}
}
代码要写得优雅，但是上面这段代码很明显是不优雅的
1注释太多；
2方法不可重用
3有丑陋的条件判断句。
4可扩展性不强
改进方法
1利用好的命名来代替注释
2使用单一功能的方法
3利用多态，及好的设计模式来解决条件判断
综上可以写出很优雅的代码，可读性与可扩展性，可维护性都会大大提高
下面是代码实现
SimpleTextTokenizer.java
import java.util.LinkedList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**The following program It tokenizes a string into its
* textual components: words, numbers,
* or punctuation. Although it is a simple example, it illustrates
* the basic techniques used to tokenize any type of input.
*/
/**
* @author chenhao
*
*/
public final class SimpleTextTokenizer {
/**
*"\G"表示前一匹配的结尾 ， "/z"表示字符串的结尾（包括）行终止符 end 用来匹配字符串的结尾.
*/
private static Pattern end = Pattern.compile("\\G\\z");
/**
* "\g\w+" 表示从前一批匹配的结尾开始匹配一个或多个可以成为单词的的. 一部分的字符. 如A - Z a-z 0 - 9 及下划线
* （单词字符)
*/
private static Pattern word = Pattern.compile("\\G\\w+");
/**
* . "/p{Punct}" 包含所有的标点符号
*/
private static Pattern punct = Pattern.compile("\\G\\p{Punct}");
/**
*"\s" 匹配空格.
*/
private static Pattern space = Pattern.compile("\\G\\s");
/**
* . 匹配数字
*/
private static Pattern number = Pattern.compile("\\G\\d+\\.?\\d*");
private SimpleTextTokenizer() { }
class InvalidToken implements TokenPrinter {
/*
* (non-Javadoc)
* @see TokenPrinter#print()
*/
public int print() {
System.out.println("invalid token");
return 0;
}
}
class EndToken implements TokenPrinter {
/* (non-Javadoc)
* @see TokenPrinter#print()
*/
public int print() {
System.out.println("End of String");
return 0;
}
}
class NormalToken implements TokenPrinter {
private String token;
public NormalToken(final String token) {
this.token = token;
}
/*
* (non-Javadoc)
* @see TokenPrinter#print()
*/
public int print() {
System.out.println("Token " + token);
return 1;
}
}
/**
* the method returns the next token retrieved from the Matcher passed to.
* @param mat
* the Matcher of the text
* @return the next token of the text
*/
static TokenPrinter getNextTokenMtchPattern(final Matcher mat) {
skipLeadingSpaces(mat);
return nextTokenMtchPattern(mat);
}
/**
* @param mat
* the matcher of a string
* @return the next token of the string
*/
private static TokenPrinter nextTokenMtchPattern(final Matcher mat) {
// Next, obtain the next token in the string
// by attempting to match each pattern.
// The token found by the first matching pattern
// is returned. The order in which the patterns
// are tried matters. Checking for a word
// before checking for a number can change the results.
// First check for a number
LinkedList<Pattern> patternList = createPatternList();
for (Pattern pat : patternList) {
mat.usePattern(pat);
if (mat.find()) {
return createTokenPrinter(mat.group());
}
}
return createTokenPrinter(null); // the patternList is null;
}
/**
* @return a linkedList of Pattern;
*/
private static LinkedList<Pattern> createPatternList() {
LinkedList<Pattern> patternList = new LinkedList<Pattern>();
patternList.add(number);
patternList.add(word);
patternList.add(punct);
patternList.add(end);
return patternList;
}
/**
* create a TokenPrinter use the token match the Pattern.
* @param token the token match the Pattern
* @return tokenPrinter
*/
private static TokenPrinter createTokenPrinter(final String token) {
SimpleTextTokenizer textTokenizer = new SimpleTextTokenizer();
if (token == null) {
return textTokenizer.new InvalidToken();
}
if (token.length() == 0) {
return textTokenizer.new EndToken();
} else {
return textTokenizer.new NormalToken(token);
}
}
/**
* @param mat
* the matcher of a string. we won't let the mat point to anther
* object so it is final
*/
private static void displayTokensInString(final Matcher mat) {
TokenPrinter tokenPtinter;
do {
tokenPtinter = getNextTokenMtchPattern(mat);
} while (tokenPtinter.print() != 0);
}
/**
* @param mat
* the matcher
*/
private static void skipLeadingSpaces(final Matcher mat) {
mat.usePattern(space);
mat.find();
}
/**
* @param args
* does nothing in this programs
*/
public static void main(final String[] args) {
// Create a matcher
Matcher mat = end.matcher("the first item is a hamer,"
+ "with a cost of $132.99.");
displayTokensInString(mat);
}
}
TokenPrinter.java
/**
* @author chenhao
* print the token itself.
*/
interface TokenPrinter {
/**
* print the token itself.
* @return the type of the token
*/
int print();
}
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