徒弟:師傅呀,正則怎麼用呀?搞個有條理性的東東給我看看吧!
師傅:也對,沒條理的東西,不懂的人,看了更加暈,先講講:字元組。
1、基本功能
字元組:
l 正規表達式的最基本結構之一
l 作用:規格某個位置能夠出現的字元
l 形式:以[...]給出,在方括号内列出字元
執行個體:
判斷10進制數值,隻要能夠判斷每個數字出現在0-9之間,那就是10進制數值。
public class GeneralNumTest {
public static void main(String[] args) {
String[] octDigits = new String[] { "0", "1", "2", "3","4","5","6","7","8","9"};
String[] hexDigits = new String[] { "0", "1", "2", "3","4","5","6","7","8","9",
"a", "b", "c", "d","e","f"};
String octDigitRegex = "[0123456789]";
String hexDigitRegex = "[0123456789abcdef]";
for (String octDigit : octDigits) {
if(regexMatch(octDigit,octDigitRegex)){
System.out.println("10進制數值:" + octDigit +"能夠比對正則:" + octDigitRegex);
}else{
System.out.println("10進制數值:" + octDigit +"不能夠能夠比對正則:" + octDigitRegex);
}
for (String hexDigit : hexDigits) {
if(regexMatch(hexDigit,hexDigitRegex)){
System.out.println("16進制數值:" + hexDigit +"能夠比對正則:" + hexDigitRegex);
System.out.println("16進制數值:" + hexDigit +"不能夠能夠比對正則:" + hexDigitRegex);
private static boolean regexMatch(String s, String regex) {
return s.matches(regex);
運作結果:
10進制數值:0能夠比對正則:[0123456789]
10進制數值:1能夠比對正則:[0123456789]
10進制數值:2能夠比對正則:[0123456789]
10進制數值:3能夠比對正則:[0123456789]
10進制數值:4能夠比對正則:[0123456789]
10進制數值:5能夠比對正則:[0123456789]
10進制數值:6能夠比對正則:[0123456789]
10進制數值:7能夠比對正則:[0123456789]
10進制數值:8能夠比對正則:[0123456789]
10進制數值:9能夠比對正則:[0123456789]
16進制數值:0能夠比對正則:[0123456789abcdef]
16進制數值:1能夠比對正則:[0123456789abcdef]
16進制數值:2能夠比對正則:[0123456789abcdef]
16進制數值:3能夠比對正則:[0123456789abcdef]
16進制數值:4能夠比對正則:[0123456789abcdef]
16進制數值:5能夠比對正則:[0123456789abcdef]
16進制數值:6能夠比對正則:[0123456789abcdef]
16進制數值:7能夠比對正則:[0123456789abcdef]
16進制數值:8能夠比對正則:[0123456789abcdef]
16進制數值:9能夠比對正則:[0123456789abcdef]
16進制數值:a能夠比對正則:[0123456789abcdef]
16進制數值:b能夠比對正則:[0123456789abcdef]
16進制數值:c能夠比對正則:[0123456789abcdef]
16進制數值:d能夠比對正則:[0123456789abcdef]
16進制數值:e能夠比對正則:[0123456789abcdef]
16進制數值:f能夠比對正則:[0123456789abcdef]
以連字元'-'表示範圍:
l [0123456789]的表示法過于累贅,可以用範圍表示法簡要描述
l [0123456789] = [0-9]
l [0-789] = [0-9]
l [0123456789abcdef] = [0-9a-f]
剛剛的例子,可以修改為:
String octDigitRegex = "[0-9]";
String hexDigitRegex = "[0-9a-f]";
關于連字元的注意事項:
l 在字元組内部,隻有當連字元出現在兩個字元之間時,才能表示字元的範圍;
l 如果出現在字元組的開頭,則隻能表示單個字元'-',就是連字元本身。
例如:
public class GeneralNumTwo {
String[] characters = new String[] { "a", "b", "c", "d","e","f","g","-"};
String regex1 = "[a-g]";
String regex2 = "[-ag]";
for (String character : characters) {
if(regexMatch(character,regex1)){
System.out.println("字元:" + character +"能夠比對正則:" + regex1);
System.out.println("字元:" + character +"不能夠能夠比對正則:" + regex1);
if(regexMatch(character,regex2)){
System.out.println("字元:" + character +"能夠比對正則:" + regex2);
System.out.println("字元:" + character +"不能夠能夠比對正則:" + regex2);
字元:a能夠比對正則:[a-g]
字元:b能夠比對正則:[a-g]
字元:c能夠比對正則:[a-g]
字元:d能夠比對正則:[a-g]
字元:e能夠比對正則:[a-g]
字元:f能夠比對正則:[a-g]
字元:g能夠比對正則:[a-g]
字元:-不能夠比對正則:[a-g]
字元:a能夠比對正則:[-ag]
字元:b不能夠比對正則:[-ag]
字元:c不能夠比對正則:[-ag]
字元:d不能夠比對正則:[-ag]
字元:e不能夠比對正則:[-ag]
字元:f不能夠比對正則:[-ag]
字元:g能夠比對正則:[-ag]
字元:-能夠比對正則:[-ag]
本文轉自jooben 51CTO部落格,原文連結:http://blog.51cto.com/jooben/317152