如果字符串應該包含';'，RegEx匹配之前和特定的字符串

Question

後，我用下面的表達式：

"?:(.*);GRAYSCALE=([0-9]{1,2}|1[0-9]{2}|2[0-4][0-9]|25[0-5])(?:;\\w*)?" 

1. Input: GRAYSCALE=(120) --> Expected output: true 
2. Input: GRAYSCALE=(120); --> Expected output: true 
3. Input: GRAYSCALE=(120);abcd --> Expected output: true 
4. Input: GRAYSCALE=(120)abcd --> Expected output: false 
5. Input: abGRAYSCALE=(120); --> Expected output: false 
6. Input: abc;GRAYSCALE=(120);acx --> Expected output: true 

對於案件1 - 4我得到正確的輸出，而不是5和6。

Answer 1

在開始處添加一個字邊界，並將第一個;作爲可選項。此外，您還必須添加模式以匹配()開啓和關閉括號。

(.*?)\\b;?GRAYSCALE=\\(([0-9]{1,2}|1[0-9]{2}|2[0-4][0-9]|25[0-5])\\)(?:;\\w*)?$ 

DEMO

String[] inputs = { 
     "GRAYSCALE=(120)",// -- Expected output: True 
     "GRAYSCALE=(120);",// -- Expected output: True 
     "GRAYSCALE=(120);abcd",// -- Expected output: True 
     "GRAYSCALE=(120)abcd",// -- Expected output: False 
     "abGRAYSCALE=(120)",// -- Expected output: False 
     "abc;GRAYSCALE=(120);acx" // --> Expected output: true 
}; 

Pattern p = Pattern.compile("(.*?)\\b;?GRAYSCALE=\\(([0-9]{1,2}|1[0-9]{2}|2[0-4][0-9]|25[0-5])\\)(?:;\\w*)?$"); 
for (String input: inputs) { 
    Matcher m = p.matcher(input); 
    System.out.printf("%s found? %b%n", input, m.find()); 
} 

輸出：

GRAYSCALE=(120) found? true 
GRAYSCALE=(120); found? true 
GRAYSCALE=(120);abcd found? true 
GRAYSCALE=(120)abcd found? false 
abGRAYSCALE=(120) found? false 
abc;GRAYSCALE=(120);acx found? true 

DEMO

Answer 2

爲什麼這麼做只有一個正則表達式？使用多種工具：

private static final Pattern SEMICOLON = Pattern.compile(";"); 
private static final Pattern GRAYSCALE 
    = Pattern.compile("GRAYSCALE=\\((\\d+\\))"); 

// Test... 
final String[] splits = SEMICOLON.split(input); 

Matcher matcher; 
boolean found = false; 
String inParens; 
int number; 

for (final String candidate: splits) { 
    matcher = GRAYSCALE.matcher(candidate); 
    if (!matcher.find()) 
     continue; 
    inParens = matcher.group(1); 
    try { 
     number = Integer.parseInt(inParens); 
     break; 
    } catch (NumberFormatException e) { 
     // overflow 
     continue; 
    } 
} 

// test "number" here 

如果使用Java 8，這裏是一些拉姆達濫用（與SEMICOLON和GRAYSCALE如上定義）：

final Optional<String> opt = SEMICOLON.splitAsStream().map(GRAYSCALE::matcher) 
    .filter(Matcher::find).map(m -> m.group(1)).findFirst(); 

if (!opt.isPresent()) { 
    // no luck 
} 

try { 
    Integer.parseInt(opt.get()); 
    // Found at least an integer 
} catch (NumberFormatException e) { 
    // overflow 
}