在文本文件中搜索多行字符串
Search for multiline String in a text file
我有一个文本文件,我正试图从中搜索包含多行的字符串。我可以搜索单个字符串,但我需要搜索多行字符串。
我试图搜索工作正常的单行。
public static void main(String[] args) throws IOException
{
File f1=new File("D:\Test\test.txt");
String[] words=null;
FileReader fr = new FileReader(f1);
BufferedReader br = new BufferedReader(fr);
String s;
String input="line one";
// here i want to search for multilines as single string like
// String input ="line one"+
// "line two";
int count=0;
while((s=br.readLine())!=null)
{
words=s.split("\n");
for (String word : words)
{
if (word.equals(input))
{
count++;
}
}
}
if(count!=0)
{
System.out.println("The given String "+input+ " is present for "+count+ " times ");
}
else
{
System.out.println("The given word is not present in the file");
}
fr.close();
}
下面是文件内容。
line one
line two
line three
line four
为此使用 StringBuilder
,从文件中读取每一行并使用 lineSeparator
将它们附加到 StringBuilder
StringBuilder lineInFile = new StringBuilder();
while((s=br.readLine()) != null){
lineInFile.append(s).append(System.lineSeparator());
}
现在使用 contains
检查 lineInFile
中的 searchString
StringBuilder searchString = new StringBuilder();
builder1.append("line one");
builder1.append(System.lineSeparator());
builder1.append("line two");
System.out.println(lineInFile.toString().contains(searchString));
试试这个,
public static void main(String[] args) throws IOException {
File f1 = new File("./src/test/test.txt");
FileReader fr = new FileReader(f1);
BufferedReader br = new BufferedReader(fr);
String input = "line one";
int count = 0;
String line;
while ((line = br.readLine()) != null) {
if (line.contains(input)) {
count++;
}
}
if (count != 0) {
System.out.println("The given String " + input + " is present for " + count + " times ");
} else {
System.out.println("The given word is not present in the file");
}
fr.close();
}
来自默认 C 的更复杂的解决方案(代码基于《The C programming language》一书中的代码)
final String searchFor = "Ich reiß der Puppe den Kopf ab\n" +
"Ja, ich reiß' ich der Puppe den Kopf ab";
int found = 0;
try {
String fileContent = new String(Files.readAllBytes(
new File("puppe-text").toPath()
));
int i, j, k;
for (i = 0; i < fileContent.length(); i++) {
for (k = i, j = 0; (fileContent.charAt(k++) == searchFor.charAt(j++)) && (j < searchFor.length());) {
// nothig
}
if (j == searchFor.length()) {
++found;
}
}
} catch (IOException ignore) {}
System.out.println(found);
为什么不将文件中的所有行规范化为一个字符串变量,然后只计算文件中输入的出现次数。我已经使用 Regex
来计算出现的次数,但可以用您认为合适的任何自定义方式来完成。
public static void main(String[] args) throws IOException
{
File f1=new File("test.txt");
String[] words=null;
FileReader fr = new FileReader(f1);
BufferedReader br = new BufferedReader(fr);
String s;
String input="line one line two";
// here i want to search for multilines as single string like
// String input ="line one"+
// "line two";
int count=0;
String fileStr = "";
while((s=br.readLine())!=null)
{
// Normalizing the whole file to be stored in one single variable
fileStr += s + " ";
}
// Now count the occurences
Pattern p = Pattern.compile(input);
Matcher m = p.matcher(fileStr);
while (m.find()) {
count++;
}
System.out.println(count);
fr.close();
}
使用 StringBuilder
class 进行高效的字符串连接。
试试 Scanner.findWithinHorizon()
String pathToFile = "/home/user/lines.txt";
String s1 = "line two";
String s2 = "line three";
String pattern = String.join(System.lineSeparator(), s1, s2);
int count = 0;
try (Scanner scanner = new Scanner(new FileInputStream(pathToFile))) {
while (scanner.hasNext()) {
String withinHorizon = scanner.findWithinHorizon(pattern, pattern.length());
if (withinHorizon != null) {
count++;
} else {
scanner.nextLine();
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
System.out.println(count);
我有一个文本文件,我正试图从中搜索包含多行的字符串。我可以搜索单个字符串,但我需要搜索多行字符串。
我试图搜索工作正常的单行。
public static void main(String[] args) throws IOException
{
File f1=new File("D:\Test\test.txt");
String[] words=null;
FileReader fr = new FileReader(f1);
BufferedReader br = new BufferedReader(fr);
String s;
String input="line one";
// here i want to search for multilines as single string like
// String input ="line one"+
// "line two";
int count=0;
while((s=br.readLine())!=null)
{
words=s.split("\n");
for (String word : words)
{
if (word.equals(input))
{
count++;
}
}
}
if(count!=0)
{
System.out.println("The given String "+input+ " is present for "+count+ " times ");
}
else
{
System.out.println("The given word is not present in the file");
}
fr.close();
}
下面是文件内容。
line one
line two
line three
line four
为此使用 StringBuilder
,从文件中读取每一行并使用 lineSeparator
StringBuilder
StringBuilder lineInFile = new StringBuilder();
while((s=br.readLine()) != null){
lineInFile.append(s).append(System.lineSeparator());
}
现在使用 contains
lineInFile
中的 searchString
StringBuilder searchString = new StringBuilder();
builder1.append("line one");
builder1.append(System.lineSeparator());
builder1.append("line two");
System.out.println(lineInFile.toString().contains(searchString));
试试这个,
public static void main(String[] args) throws IOException {
File f1 = new File("./src/test/test.txt");
FileReader fr = new FileReader(f1);
BufferedReader br = new BufferedReader(fr);
String input = "line one";
int count = 0;
String line;
while ((line = br.readLine()) != null) {
if (line.contains(input)) {
count++;
}
}
if (count != 0) {
System.out.println("The given String " + input + " is present for " + count + " times ");
} else {
System.out.println("The given word is not present in the file");
}
fr.close();
}
来自默认 C 的更复杂的解决方案(代码基于《The C programming language》一书中的代码)
final String searchFor = "Ich reiß der Puppe den Kopf ab\n" +
"Ja, ich reiß' ich der Puppe den Kopf ab";
int found = 0;
try {
String fileContent = new String(Files.readAllBytes(
new File("puppe-text").toPath()
));
int i, j, k;
for (i = 0; i < fileContent.length(); i++) {
for (k = i, j = 0; (fileContent.charAt(k++) == searchFor.charAt(j++)) && (j < searchFor.length());) {
// nothig
}
if (j == searchFor.length()) {
++found;
}
}
} catch (IOException ignore) {}
System.out.println(found);
为什么不将文件中的所有行规范化为一个字符串变量,然后只计算文件中输入的出现次数。我已经使用 Regex
来计算出现的次数,但可以用您认为合适的任何自定义方式来完成。
public static void main(String[] args) throws IOException
{
File f1=new File("test.txt");
String[] words=null;
FileReader fr = new FileReader(f1);
BufferedReader br = new BufferedReader(fr);
String s;
String input="line one line two";
// here i want to search for multilines as single string like
// String input ="line one"+
// "line two";
int count=0;
String fileStr = "";
while((s=br.readLine())!=null)
{
// Normalizing the whole file to be stored in one single variable
fileStr += s + " ";
}
// Now count the occurences
Pattern p = Pattern.compile(input);
Matcher m = p.matcher(fileStr);
while (m.find()) {
count++;
}
System.out.println(count);
fr.close();
}
使用 StringBuilder
class 进行高效的字符串连接。
试试 Scanner.findWithinHorizon()
String pathToFile = "/home/user/lines.txt";
String s1 = "line two";
String s2 = "line three";
String pattern = String.join(System.lineSeparator(), s1, s2);
int count = 0;
try (Scanner scanner = new Scanner(new FileInputStream(pathToFile))) {
while (scanner.hasNext()) {
String withinHorizon = scanner.findWithinHorizon(pattern, pattern.length());
if (withinHorizon != null) {
count++;
} else {
scanner.nextLine();
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
System.out.println(count);