标准的正则表达式是什么样的
Node.js(JavaScript)
在正则表达式中，斜杠（/）用来表示正则表达式的开始和结束。在JavaScript中，正则表达式可以使用斜杠包裹起来，以表示这是一个正则表达式的字面量。
在Node.js中，可以使用正则表达式的test()方法来检查一个字符串是否匹配某个模式。以下是一个示例代码，演示了如何使用正则表达式匹配以1开头，后面跟着两个数字的字符串：
const str = '123';
const regex = /^1\d{2}$/;
if (regex.test(str)) {
console.log('匹配成功');
} else {
console.log('匹配失败');
}
在上面的示例中，^1\d{2}$是一个正则表达式，它的含义是：
^：匹配字符串的开头
1：匹配字符1
\d{2}：匹配两个数字（\d表示任意数字，{2}表示匹配两次）
$：匹配字符串的结尾
因此，该正则表达式可以匹配以1开头，后面跟着两个数字的字符串。在示例中，str的值为123，它符合这个模式，所以输出结果为匹配成功。
Java
private void RegTest2() {
String content ="abc$(abc(1.23(";
//匹配(
String regStr = "\\d{2}";
// String regStr = "\\.";
Pattern pattern = Pattern.compile(regStr);
Matcher matcher = pattern.matcher(content);
while (matcher.find()){
Log.i(TAG,"match:" + matcher.group(0));
}
}
2023-08-11 17:49:18.021 27898-29062/cn.jj.reg I/JJWorld.MainActivity: match:23
结论
不同语言正则表达式有区别，缺乏统一的正则标准。
ASCII码表
java中合法表示字符串中转义符的方式
java读取文件assets中ini文件时，转义符消失的问题
java读取文件时，分为了三步。
第一步通过inputStream获取输入流。
如果将读取到的数据依次打印的话，可以看到是读取到了转移字符的
Properties properties = IniPropertiesReadUtils.loadFileFromAssetsNew(this, "jjapm1.ini");
//读取Assets目录下的配置文件
public static Properties loadFileFromAssetsNew(Context context, String filePath) {
if (null == context || null == filePath || filePath.length() == 0)
return null;
InputStream assetFileIS = null;
InputStreamReader assetFileISReader = null;
Properties properties = new Properties();
int readData = 0;
try {
assetFileIS = context.getResources().getAssets().open(filePath);
while ((readData = assetFileIS.read())!= -1){
Log.i(TAG,"read:" + (char)readData);
}
} catch (IOException e) {
e.printStackTrace();
properties = null;
} finally {
try {
if (null != assetFileIS) {
assetFileIS.close();
}
if (null != assetFileISReader) {
assetFileISReader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return properties;
}
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:c
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:l
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:a
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:s
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:s
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:R
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:u
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:l
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:e
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:=
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:ä
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:¸
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:{
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:\
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:d
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:\
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:d
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:"
2023-08-12 10:05:26.258 27428-27460/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read:}
上面打印的控制信息不管，可见是打印出来了classRule = 中{\d\d"}的，只不过中文是乱码。
第二步 通过InputStreamReader获取输入字符流，处理乱码问题
//读取Assets目录下的配置文件
public static Properties loadFileFromAssetsNew(Context context, String filePath) {
if (null == context || null == filePath || filePath.length() == 0)
return null;
InputStream assetFileIS = null;
InputStreamReader assetFileISReader = null;
Properties properties = new Properties();
int readData = 0;
try {
assetFileIS = context.getResources().getAssets().open(filePath);
// while ((readData = assetFileIS.read())!= -1){
// Log.i(TAG,"read:" + (char)readData);
// }
assetFileISReader = new InputStreamReader(assetFileIS, "UTF-8");
while ((readData = assetFileISReader.read())!= -1){
Log.i(TAG,"read11:" + (char)readData);
}
} catch (IOException e) {
e.printStackTrace();
properties = null;
} finally {
try {
if (null != assetFileIS) {
assetFileIS.close();
}
if (null != assetFileISReader) {
assetFileISReader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return properties;
}
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:c
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:l
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:a
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:s
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:s
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:R
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:u
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:l
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:e
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:=
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:中
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:{
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:\
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:d
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:\
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:d
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:"
2023-08-12 10:06:52.827 27565-27600/cn.jj.reg I/JJWorld.IniPropertiesReadUtils: read11:}
转义符依然是存在的，classRule = 中{\d\d"}
第三步 properties.load(assetFileISReader)对转义符进行了特殊处理，导致转义符失效
JSONObject对转义符的处理
private void jsonRegTest() throws JSONException {
String jsonStr = "{key:\"va\\lue\"}";
// JSONObject对\的处理
JSONObject jsonObject = new JSONObject(jsonStr);
Log.i(TAG, "jsonRegTest:" + jsonObject.toString());
}
public JSONObject(@NonNull String json) throws JSONException {
this(new JSONTokener(json));
}
new JSONObject会创建一个JSONTokener。JSONTokener保留设置进来的字符串。文章来源：https://www.toymoban.com/news/detail-653517.html
public JSONTokener(String in) {
// consume an optional byte order mark (BOM) if it exists
if (in != null && in.startsWith("\ufeff")) {
in = in.substring(1);
}
this.in = in;
}
JSONObject(String)核心代码
public JSONObject(@NonNull JSONTokener readFrom) throws JSONException {
/*
* Getting the parser to populate this could get tricky. Instead, just
* parse to temporary JSONObject and then steal the data from that.
*/
Object object = readFrom.nextValue();
if (object instanceof JSONObject) {
this.nameValuePairs = ((JSONObject) object).nameValuePairs;
} else {
throw JSON.typeMismatch(object, "JSONObject");
}
}
文章来源地址https://www.toymoban.com/news/detail-653517.html
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