Regular expression hangs - Java matcher

Question

String:

Aqua, Sodium Laureth Sulfate, Sodium Lauryl Sulfate, Dimethicone, Cocamide MEA, Zinc Carbonate, Glycol Distearate, Sodium Chloride, Zinc Pyrithion

Answer 1

Perhaps what you had in mind was

String regex = "([A-Z][\\d\\w]+( [A-Z][-\\d\\w]+)*, )*[A-Z][-\\d\\w]+( [A-Z][-\\d\\w]+)*\\.";
System.out.println(string.matches(regex));

returns true.

The problem you have with the regex is that its overly complicated. The disadvantage with adding expressions until you get true is that it can match things you didn't have in mind.

Random rand = new Random();
while(true) {
    byte[] bytes = new byte[40];
    rand.nextBytes(bytes);
    for (int i = 0; i < bytes.length; i++) bytes[i] &= 0x7F;
    String string = new String(bytes, 0);
    if (string.matches("([\\W]*\\b[A-Z\\d]\\w+\\b[\\W\\d]*)+"))
        System.out.println(string);
}

prints things such as

"^;%XX`'SwJ|[*4"*0C7`LHsCN*,{26O}
EFJ5MBVxi%W_t6v54EmLmgjFvqyYh\<"
+7]|ULh2[MT`Yx{MKH4N
'8p!2mf

whereas the expression I gave matches

KfhBuGv7, S3.
IWzu, XHop4Z.
LJbXfrd, PdR.
V2dxQV, LA9z.
HKf37cy0, TS.
RAw2E5a, Ajs.
Up-, GPQ7 I_.