在Java中使用正則表達式
jdk1.4中加入了java.util.regex包提供對正則表達式的支持。而且Java.lang.String類中的replaceAll和split函數也是調用的正則表達式來實現的。
正則表達式對字符串的操作主要包括：字符串匹配，指定字符串替換，指定字符串查找和字符串分割。下面就用一個例子來說明這些操作是如何實現的：
| ＜%@ page import="java.util.regex.*"%＞ ＜% Pattern p=null; //正則表達式 Matcher m=null; //操作的字符串 boolean b; String s=null; StringBuffer sb=null; int i=0; //字符串匹配，這是不符合的 p = Pattern.compile("a*b"); m = p.matcher("baaaaab"); b = m.matches(); out.println(b+"＜br＞"); //字符串匹配，這是符合的 p = Pattern.compile("a*b"); m = p.matcher("aaaaab"); b = m.matches(); out.println(b+"＜br＞"); //字符串替換 p = Pattern.compile("ab"); m = p.matcher("aaaaab"); s = m.replaceAll("d"); out.println(s+"＜br＞"); p = Pattern.compile("a*b"); m = p.matcher("aaaaab"); s = m.replaceAll("d"); out.println(s+"＜br＞"); p = Pattern.compile("a*b"); m = p.matcher("caaaaab"); s = m.replaceAll("d"); out.println(s+"＜br＞"); //字符串查找 p = Pattern.compile("cat"); m = p.matcher("one cat two cats in the yard"); sb = new StringBuffer(); while (m.find()) { m.appendReplacement(sb, "dog"); i++; } m.appendTail(sb); out.println(sb.toString()+"＜br＞"); out.println(i+"＜br＞"); i=0; p = Pattern.compile("cat"); m = p.matcher("one cat two ca tsi nthe yard"); sb = new StringBuffer(); while (m.find()) { m.appendReplacement(sb, "dog"); i++; } m.appendTail(sb); out.println(sb.toString()+"＜br＞"); out.println(i+"＜br＞"); p = Pattern.compile("cat"); m = p.matcher("one cat two cats in the yard"); p=m.pattern(); m = p.matcher("bacatab"); b = m.matches(); out.println(b+"＜br＞"); s = m.replaceAll("dog"); out.println(s+"＜br＞"); i=0; p = Pattern.compile("(fds){2,}"); m = p.matcher("dsa da fdsfds aaafdsafds aaf"); sb = new StringBuffer(); while (m.find()) { m.appendReplacement(sb, "dog"); i++; } m.appendTail(sb); out.println(sb.toString()+"＜br＞"); out.println(i+"＜br＞"); p = Pattern.compile("cat"); m = p.matcher("one cat two cats in the yard"); sb = new StringBuffer(); while (m.find()) { m.appendReplacement(sb, "＜font color="red"＞cat＜/font＞"); } m.appendTail(sb); out.println(sb.toString()+"＜br＞"); String aa=sb.toString(); out.println(aa+"＜br＞"); //字符串分割 p = Pattern.compile("a+"); String[] a=p.split("caaaaaat"); for(i=0;i＜a.length;i++) { out.println(a[i]+"＜br＞"); } p = Pattern.compile("a+"); a=p.split("c aa aaaa t",0); for(i=0;i＜a.length;i++) { out.println(a[i]+"＜br＞"); } p = Pattern.compile(" +"); a=p.split("c aa aaaa t",0); for(i=0;i＜a.length;i++) { out.println(a[i]+"＜br＞"); } p = Pattern.compile("\+"); a=p.split("dsafasdfdsafsda+dsagfasdfa+sdafds"); out.println(a.length+"＜br＞"); for(i=0;i＜a.length;i++) { out.println(a[i]+"＜br＞"); } %＞ |