从Java中的文件中删除多行中的一行

Question

I have to remove all the single lines from a file that contains multiple lines. For example, suppose I have the input file like below,

file1.txt

ALTER TABLE <tablename>
MODIFY <some parameter>
    
ALTER TABLE <tablename> #this is a single line, so need to remove this

ALTER TABLE <tablename> #this is a single line, so need to remove this

ALTER TABLE <tablename>
MODIFY <some parameter>

ALTER TABLE <tablename> #this is a single line, so need to remove this

The output file should contain only the below lines,

file2.txt

ALTER TABLE <tablename>
MODIFY <some parameter>

ALTER TABLE <tablename>
MODIFY <some parameter>

Any help would be appreciated.

Answer 1

here some ideas might help you.

1. when it's not first or last.make sure the line that before and after itself is empty then pass it

2. when it's first or last. make sure when first after this is empty and the logic of last is the same.

FileReader fileReader = new FileReader("/data/xx.text");
BufferedReader bufferedReader = new BufferedReader(fileReader);
List<String> lines = bufferedReader.lines().collect(Collectors.toList());
List<String> finalLines = new ArrayList<>();
if(lines.size() == 1){
    // it's empty
    return;
}
if(lines.size() == 2 && (lines.get(0)== null ||lines.get(1) == null)){
    return;
}
for (int i = 1; i < lines.size() - 1; i++) {
    if(i == 1 && lines.get(i + 1) == null){
        continue;
    }
    if(lines.get(i-1) == null && lines.get(i + 1) == null && lines.get(i) != null){
        continue;
    }

    finalLines.add(lines.get(i));
}
if(lines.get(lines.size() - 2) != null){
    finalLines.add(lines.get(lines.size() -1));
}
for (String finalLine : finalLines) {
    System.out.println(finalLine);
}