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java.lang.UnsupportedClassVersionError: Bad version number in .class file?
...ting this error when I include an opensource library that I had to compile from source. Now, all the suggestions on the web indicate that the code was compiled in one version and executed in another version (new on old). However, I only have one version of JRE on my system. If I run the commands:...
How to uncommit my last commit in Git [duplicate]
...
@Jefromi: every answer in this question is totally wrong to emphasize --hard, the --soft, is necessary for it to be "uncommit last commit", a --hard will not only uncommit but also destroy your commit. I nearly destroyed a whol...
How to read all files in a folder from Java?
...e/you/Desktop");
listFilesForFolder(folder);
Files.walk API is available from Java 8.
try (Stream<Path> paths = Files.walk(Paths.get("/home/you/Desktop"))) {
paths
.filter(Files::isRegularFile)
.forEach(System.out::println);
}
The example uses try-with-resources patte...
cartesian product in pandas
... you can produce a cartesian product using merge (like you would in SQL).
from pandas import DataFrame, merge
df1 = DataFrame({'key':[1,1], 'col1':[1,2],'col2':[3,4]})
df2 = DataFrame({'key':[1,1], 'col3':[5,6]})
merge(df1, df2,on='key')[['col1', 'col2', 'col3']]
Output:
col1 col2 col3
0 ...
How can I lock a file using java (if possible)
... opens a file using a FileReader. How can I prevent another (Java) process from opening this file, or at least notify that second process that the file is already opened? Does this automatically make the second process get an exception if the file is open (which solves my problem) or do I have to ex...
How can I check file size in Python?
....stat. You can get it by either using pathlib (Python 3.4+):
>>> from pathlib import Path
>>> Path('somefile.txt').stat()
os.stat_result(st_mode=33188, st_ino=6419862, st_dev=16777220, st_nlink=1, st_uid=501, st_gid=20, st_size=1564, st_atime=1584299303, st_mtime=1584299400, st_ct...
When to use PNG or JPG in iPhone development?
... extra CPU energy to display. However, large PNGs may take longer to read from storage than more compressed image formats, and thus be slower to display.
JPG's are smaller to store, but lossy (amount depends on compression level), and to display them requires a much more complicated decoding algor...
How to override trait function and call it from the overridden function?
...n calc($v) {
return parent::calc($v*3);
}
}
// .... other code from above
print (new MyTraitChildClass())->calc(2); // will print 8 (2*3 + 2)
You can also provide for ways to override, but still access the trait method as follows:
trait A {
function trait_calc($v) {
ret...
Repository Pattern Step by Step Explanation [closed]
...ects are persisted. All of the knowledge of persistence, including mapping from tables to objects, is safely contained in the repository.
Very often, you will find SQL queries scattered in the codebase and when you come to add a column to a table you have to search code files to try and find usages...
What do the terms “CPU bound” and “I/O bound” mean?
...ght become I/O bound, since the bottleneck is then the reading of the data from disk (actually, this example is perhaps kind of old-fashioned these days with hundreds of MB/s coming in from SSDs).
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