Java 使用Collections.sort进行比较
我尝试对一个文本文件进行排序,该文件由制表符分隔,并尝试按第三个字段className进行排序。然后我将在一张表中显示它。我写了以下部分,但排序不正确。你知道我错在哪里吗Java 使用Collections.sort进行比较,java,sorting,collections,comparator,Java,Sorting,Collections,Comparator,我尝试对一个文本文件进行排序,该文件由制表符分隔,并尝试按第三个字段className进行排序。然后我将在一张表中显示它。我写了以下部分,但排序不正确。你知道我错在哪里吗 public void sortFile(){ BufferedReader reader = null; BufferedWriter writer = null; //Create an ArrayList object to hold the lines of input file
public void sortFile(){
BufferedReader reader = null;
BufferedWriter writer = null;
//Create an ArrayList object to hold the lines of input file
ArrayList<String> lines = new ArrayList<>();
try{
//Creating BufferedReader object to read the input file
reader = new BufferedReader(new FileReader("pupilInfo.txt"));
//Reading all the lines of input file one by one and adding them into ArrayList
String currentLine = reader.readLine();
while (currentLine != null){
lines.add(currentLine);
currentLine = reader.readLine();
}
Collections.sort(lines, (String s1, String s2) -> {
s1 = lines.get(0);
s2 = lines.get(1);
String [] line1 = s1.split("\t");
String [] line2 = s2.split("\t");
String classNameLine1 = line1[2];
String classNameLine2 = line2[2];
System.out.println("classname1=" + classNameLine1);
System.out.println("classname2=" + classNameLine2);
int sComp = classNameLine1.compareTo(classNameLine2);
return sComp;
});
//Creating BufferedWriter object to write into output temp file
writer = new BufferedWriter(new FileWriter("pupilSortTemp.txt"));
//Writing sorted lines into output file
for (String line : lines){
writer.write(line);
writer.newLine();
}
}catch (IOException e){
}
finally{
//Closing the resources
try{
if (reader != null){
reader.close();
}
if(writer != null){
writer.close();
}
}catch (IOException e){
}
}
}
我用comparator试过了。为了简单起见,我的源文件如下
public void sortFile(){
BufferedReader reader = null;
BufferedWriter writer = null;
//Create an ArrayList object to hold the lines of input file
ArrayList<String> lines = new ArrayList<>();
try{
//Creating BufferedReader object to read the input file
reader = new BufferedReader(new FileReader("pupilInfo.txt"));
//Reading all the lines of input file one by one and adding them into ArrayList
String currentLine = reader.readLine();
while (currentLine != null){
lines.add(currentLine);
currentLine = reader.readLine();
}
Collections.sort(lines, (String s1, String s2) -> {
s1 = lines.get(0);
s2 = lines.get(1);
String [] line1 = s1.split("\t");
String [] line2 = s2.split("\t");
String classNameLine1 = line1[2];
String classNameLine2 = line2[2];
System.out.println("classname1=" + classNameLine1);
System.out.println("classname2=" + classNameLine2);
int sComp = classNameLine1.compareTo(classNameLine2);
return sComp;
});
//Creating BufferedWriter object to write into output temp file
writer = new BufferedWriter(new FileWriter("pupilSortTemp.txt"));
//Writing sorted lines into output file
for (String line : lines){
writer.write(line);
writer.newLine();
}
}catch (IOException e){
}
finally{
//Closing the resources
try{
if (reader != null){
reader.close();
}
if(writer != null){
writer.close();
}
}catch (IOException e){
}
}
}
pippo;pluto;paperino
casa;terra;cortile
primo;secondo;terzo
Comparator<String> comparator = new Comparator<String>() {
@Override
public int compare(String o1, String o2) {
return o1.split(";")[2].compareTo(o2.split(";")[2]);
}
};
lines.sort(comparator);
在第三栏排序 s1=lines.get0;s2=lines.get1;-你到底在干什么?如果删除@user2357112识别的两行,这将是解决问题的良好开端。传递给Collections.sort的比较器已在要从ArrayList进行比较的字符串中传递,因此不需要手动设置它们。此外,您实际上正在覆盖传递给比较器的正确值。我对这一点不熟悉。我取出了上面提到的那几行。谢谢你的评论。非常感谢。我要去一个初学者论坛。我想也许我会在这里得到一些帮助。谢谢你友好地回答我的问题。这个选项适合我。
public void sortFile(){
BufferedReader reader = null;
BufferedWriter writer = null;
//Create an ArrayList object to hold the lines of input file
ArrayList<String> lines = new ArrayList<>();
try{
//Creating BufferedReader object to read the input file
reader = new BufferedReader(new FileReader("pupilInfo.txt"));
//Reading all the lines of input file one by one and adding them into ArrayList
String currentLine = reader.readLine();
while (currentLine != null){
lines.add(currentLine);
currentLine = reader.readLine();
}
Collections.sort(lines, (String s1, String s2) -> {
s1 = lines.get(0);
s2 = lines.get(1);
String [] line1 = s1.split("\t");
String [] line2 = s2.split("\t");
String classNameLine1 = line1[2];
String classNameLine2 = line2[2];
System.out.println("classname1=" + classNameLine1);
System.out.println("classname2=" + classNameLine2);
int sComp = classNameLine1.compareTo(classNameLine2);
return sComp;
});
//Creating BufferedWriter object to write into output temp file
writer = new BufferedWriter(new FileWriter("pupilSortTemp.txt"));
//Writing sorted lines into output file
for (String line : lines){
writer.write(line);
writer.newLine();
}
}catch (IOException e){
}
finally{
//Closing the resources
try{
if (reader != null){
reader.close();
}
if(writer != null){
writer.close();
}
}catch (IOException e){
}
}
}