在用逗号分隔行之后，用空格分隔该行中的每个字段，并取最后一个元素。

currentline = br.readline()
… for each line of input 
List< String > newFields= new ArrayList<>() ;
String[] fieldsOfRow = currentline.split(",");
for( String field : fieldsOfRow )
{
    String[] partsOfField = field.split( " " ) ;
    String lastPart = partsOfField[ partsOfField.length - 1 ] ;
    newFields.add( lastPart ) ;
    …
}
String newLine = String.join( "," , newFields ) ;

我没有足够的声誉发表评论，但看起来您可能需要进一步拆分字符串数组arraystrfilerows中的字符串，并将所需的值附加到要打印的新字符串中。

arrayStrFileRows = currentline.split(",");
String result ="";

for (int i=0; i<arrayStrFileRows.length(); i++){
    String[] tokens = arrayStrFileRows.split(" ");
    if (i ==0){
         result = tokens[2]    //i m not too sure about this since there are 3 words/numbers before your first comma and is the 1 supposed to be there or not?
    }else{
         result = result +","+token[1];
    }
}

}