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How to check if an object is nullable?
How do I check if a given object is nullable in other words how to implement the following method...
14 Answers
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Error in if/while (condition) {: missing Value where TRUE/FALSE needed
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The evaluation of condition resulted in an NA. The if conditional must have either a TRUE or FALSE result.
if (NA) {}
## Error in if (NA) { : missing value where TRUE/FALSE needed
This can happen accidentally as the results of calculations:
if(TRUE && sqrt(-1)) ...
Does java.util.List.isEmpty() check if the list itself is null? [duplicate]
Does java.util.List.isEmpty() check if the list itself is null , or do I have to do this check myself?
8 Answers
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Check if a path represents a file or a folder
I need a valid method to check if a String represents a path for file or a directory. What are valid directory names in Android? As it comes out, folder names can contain '.' chars, so how does system understand whether there's a file or a folder?
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Create a folder if it doesn't already exist
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Try this, using mkdir:
if (!file_exists('path/to/directory')) {
mkdir('path/to/directory', 0777, true);
}
Note that 0777 is already the default mode for directories and may still be modified by the current umask.
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Assign variable value inside if-statement [duplicate]
...can be assigned but not declared inside the conditional statement:
int v;
if((v = someMethod()) != 0) return true;
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Check if string contains only whitespace
How can I test if a string contains only whitespace?
11 Answers
11
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Check if a program exists from a Makefile
How can I check if a program is callable from a Makefile?
12 Answers
12
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How do you check if a certain index exists in a table?
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You can also wrap the statement into a IF EXISTS(SELECT * ...) BEGIN ... END.
– bounav
Sep 23 '13 at 9:10
27
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Check if directory mounted with bash
.... From a shell script, you can check for the mount point with grep and an if-statement:
if mount | grep /mnt/md0 > /dev/null; then
echo "yay"
else
echo "nay"
fi
In my example, the if-statement is checking the exit code of grep, which indicates if there was a match. Since I don't want...