我的任务是从输入文件test.txt
中读取,该文本有一些句子。
我需要编写一个带有构造函数和三个方法的类。
其中之一必须颠倒句子中单词的顺序。
import java.util.*;
import java.io.*;
public class Reverser {
Scanner sc3 = null ;
//constructor takes input file and initialize scanner sc pointing at input
public Reverser(File file)throws FileNotFoundException, IOException{
sc3 = new Scanner (file);
}
//this method reverses the order of the words in each line of the input
//and prints it to output file specified in argument.
public void reverseEachLine(File outpr)throws FileNotFoundException, IOException{
// ArrayList<String> wordsarraylist = new ArrayList<String>();
while(sc3.hasNextLine()){
String sentence = sc3.nextLine();
// int length = sentence.length();
String[] words = sentence.split(" ");
// wordsarraylist.clear();
List<String> wordsarraylist = new ArrayList<String>(Arrays.asList(words));
Collections.reverse(wordsarraylist);
FileWriter writer = new FileWriter(outpr,true);
for(String str: wordsarraylist) {
writer.write(str + " ");
}
writer.write(System.lineSeparator());
writer.close();
}
}
}
我已经删除了另外两种方法,但它们不会干扰这个方法。 这是我的主要内容:
import java.io.*;
public class DemoReverser {
public static void main (String [] args)
throws IOException, FileNotFoundException {
Reverser r = new Reverser(new File("test.txt"));
r.reverseEachLine(new File("out2.txt"));
}
}
问题是在执行结束时我的输出文件包含相同的内容。这并不是颠倒顺序。怎么会? Collections.reverse()
不会颠倒顺序吗?所以当我打印它时,我应该把单词颠倒过来?
我还需要使用 arraylist。
这是我的输入文件:
This is just a small file. That
has some lines of text.
If we are successful, these
lines will be
reversed.
Let's hope for the best!
我应该在我的输出中得到这个:
That file. small a just is This
text. of lines some has
these successful, are we If
be will lines
reversed.
best! the for hope Let's
但是我得到了这个:
This is just a small file. That
has some lines of text.
If we are successful, these
lines will be
reversed.
Let's hope for the best!
最佳答案
尝试一下方法 reverseEachLine
的代码,它工作得很好。不要在构造函数中构造 Scanner
。
公共(public)类 MyReverser {
private File inputFile;
public MyReverser(File file) {
this.inputFile = file;
}
public void reverseEachLine(File outpr) throws FileNotFoundException, IOException {
Scanner sc = new Scanner(inputFile);
ArrayList<List<String>> wordsarraylist = new ArrayList<List<String>>();
while (sc.hasNextLine()) {
String sentence = sc.nextLine();
List words = Arrays.asList(sentence.split(" "));
Collections.reverse(words);
wordsarraylist.add(words);
}
FileWriter writer = new FileWriter(outpr, false);
for (List<String> list : wordsarraylist) {
for (String string : list) {
writer.append(string + " ");
}
writer.append(System.lineSeparator());
}
writer.flush();
writer.close();
}
}
我已经在这里回答了完整的代码 java cannot create file by 3 methods
关于java - 反转数组列表无法正常工作,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/32754227/