我如何使用“."作为java中String.split()的分隔符 [英] How can I use "." as the delimiter with String.split() in java
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问题描述
我想要做的是读取一个 .java 文件，然后挑选出所有标识符并将它们存储在一个列表中.我的问题是 .split() 方法.如果您按原样运行此代码，您将获得 ArrayOutOfBounds，但如果您将分隔符从."更改为.".对于其他任何事情，代码都有效.但我需要用."解析的行.那么我还有其他方法可以做到这一点吗?
What I am trying to do is read a .java file, and pick out all of the identifiers and store them in a list. My problem is with the .split() method. If you run this code the way it is, you will get ArrayOutOfBounds, but if you change the delimiter from "." to anything else, the code works. But I need to lines parsed by "." so is there another way I could accomplish this?
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.*;
public class MyHash {
private static String[] reserved = new String[100];
private static List list = new LinkedList();
private static List list2 = new LinkedList();
public static void main (String args[]){
Hashtable hashtable = new Hashtable(997);
makeReserved();
readFile();
String line;
ListIterator itr = list.listIterator();
int listIndex = 0;
while (listIndex < list.size()) {
if (itr.hasNext()){
line = itr.next().toString();
//PROBLEM IS HERE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
String[] words = line.split("."); //CHANGE THIS AND IT WILL WORK
System.out.println(words[0]); //TESTING TO SEE IF IT WORKED
}
listIndex++;
}
}
public static void readFile() {
String text;
String[] words;
BufferedReader in = null;
try {
in = new BufferedReader(new FileReader("MyHash.java")); //NAME OF INPUT FILE
} catch (FileNotFoundException ex) {
Logger.getLogger(MyHash.class.getName()).log(Level.SEVERE, null, ex);
}
try {
while ((text = in.readLine()) != null){
text = text.trim();
words = text.split("\s+");
for (int i = 0; i < words.length; i++){
list.add(words[i]);
}
for (int j = 0; j < reserved.length; j++){
if (list.contains(reserved[j])){
list.remove(reserved[j]);
}
}
}
} catch (IOException ex) {
Logger.getLogger(MyHash.class.getName()).log(Level.SEVERE, null, ex);
}
try {
in.close();
} catch (IOException ex) {
Logger.getLogger(MyHash.class.getName()).log(Level.SEVERE, null, ex);
}
}
public static int keyIt (int x) {
int key = x % 997;
return key;
}
public static int horner (String word){
int length = word.length();
char[] letters = new char[length];
for (int i = 0; i < length; i++){
letters[i]=word.charAt(i);
}
char[] alphabet = new char[26];
String abc = "abcdefghijklmnopqrstuvwxyz";
for (int i = 0; i < 26; i++){
alphabet[i]=abc.charAt(i);
}
int[] numbers = new int[length];
int place = 0;
for (int i = 0; i < length; i++){
for (int j = 0; j < 26; j++){
if (alphabet[j]==letters[i]){
numbers[place]=j+1;
place++;
}
}
}
int hornered = numbers[0] * 32;
for (int i = 1; i < numbers.length; i++){
hornered += numbers[i];
if (i == numbers.length -1){
return hornered;
}
hornered = hornered % 997;
hornered *= 32;
}
return hornered;
}
public static String[] makeReserved (){
reserved[0] = "abstract";
reserved[1] = "assert";
reserved[2] = "boolean";
reserved[3] = "break";
reserved[4] = "byte";
reserved[5] = "case";
reserved[6] = "catch";
reserved[7] = "char";
reserved[8] = "class";
reserved[9] = "const";
reserved[10] = "continue";
reserved[11] = "default";
reserved[12] = "do";
reserved[13] = "double";
reserved[14] = "else";
reserved[15] = "enum";
reserved[16] = "extends";
reserved[17] = "false";
reserved[18] = "final";
reserved[19] = "finally";
reserved[20] = "float";
reserved[21] = "for";
reserved[22] = "goto";
reserved[23] = "if";
reserved[24] = "implements";
reserved[25] = "import";
reserved[26] = "instanceof";
reserved[27] = "int";
reserved[28] = "interface";
reserved[29] = "long";
reserved[30] = "native";
reserved[31] = "new";
reserved[32] = "null";
reserved[33] = "package";
reserved[34] = "private";
reserved[35] = "protected";
reserved[36] = "public";
reserved[37] = "return";
reserved[38] = "short";
reserved[39] = "static";
reserved[40] = "strictfp";
reserved[41] = "super";
reserved[42] = "switch";
reserved[43] = "synchronize";
reserved[44] = "this";
reserved[45] = "throw";
reserved[46] = "throws";
reserved[47] = "trasient";
reserved[48] = "true";
reserved[49] = "try";
reserved[50] = "void";
reserved[51] = "volatile";
reserved[52] = "while";
reserved[53] = "=";
reserved[54] = "==";
reserved[55] = "!=";
reserved[56] = "+";
reserved[57] = "-";
reserved[58] = "*";
reserved[59] = "/";
reserved[60] = "{";
reserved[61] = "}";
return reserved;
}
}
推荐答案
String.split 接受一个正则表达式，和 '.'对正则表达式有特殊意义.
String.split takes a regex, and '.' has a special meaning for regexes.
你(可能)想要这样的东西:
You (probably) want something like:
String[] words = line.split("\.");
有些人似乎无法让它工作，所以这里有一些可运行的代码，您可以用来验证正确的行为.
Some folks seem to be having trouble getting this to work, so here is some runnable code you can use to verify correct behaviour.
import java.util.Arrays;
public class TestSplit {
public static void main(String[] args) {
String line = "aa.bb.cc.dd";
String[] words = line.split("\.");
System.out.println(Arrays.toString(words));
// Output is "[aa, bb, cc, dd]"
}
}
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