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Server Side Programming Articles
Page 1147 of 2109
Can we define an enum inside a method in Java?
Enumerations in Java represents a group of named constants, you can create an enumeration using the following syntax −enum Days { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY }We can an enumeration inside a class. But, we cannot define an enum inside a method. If you try to do so it generates a compile time error saying “enum types must not be local”.Examplepublic class EnumExample{ public void sample() { enum Vehicles { Activa125, Activa5G, Access125, Vespa, TVSJupiter; } } }ErrorEnumExample.java:3: error: enum types must not be local ...
Read MoreHow to convert a double value into a Java String using append method?
The append method of the StringBuilder or StringBuffer objects accept a boolean or, char or, char array or, double or, float or, int or, long or, String value as parameter and adds it to the current object.You can append the required double value to the method and retrieve a String from obtained StringBuffer (or, StringBuilder) objects.Exampleimport java.util.Scanner; public class ConversionOfDouble { public static void main(String args[]) { Scanner sc = new Scanner(System.in); System.out.println("Enter a double value:"); double d = sc.nextDouble(); StringBuffer sb = new StringBuffer(); sb.append(d); ...
Read MoreHow to create a single data frame from data frames stored in a list with row names in R?
If we have multiples data frames of same size stored in a list and we believe that these data frames have similar characteristic then we can create a single data frame. This can be done with the help of do.call. For example, if we have a list defined with the name List containing data frames with equal number of rows with their names then a single data frame can be created do.call(rbind,unname(List)).Exampledf1
Read MoreHow to convert columns of an R data frame into a single vector?
Sometimes all the columns in a data frame have similar data characteristics representing a particular variable. For example, having a data frame containing five columns each with heights of people. To convert this type of data frame into a vector we can use as.vector function along with the as.matrix function. The as.matrix will read the data frame columns so that the array of values can be created.Example1y1
Read MoreHow to select positive values in an R data frame column?
We know that positive values are greater thandf1$x[which(df1$x>0)]Example1set.seed(254) x
Read MoreHow to save a plot in pdf in R?
To save a plot in pdf, we can use the pdf function in base R. For example, if we want to save a plot with the name PDF then it can be done using the below command −pdf("PDF.pdf")After this we can create the plot and use dev.off().Examplepdf("pdfExample.pdf") plot(1:10)OutputExampledev.off()OutputTo check where it is saved, find the working directory using getwd().
Read MoreCan we override default methods in Java?
An interface in Java is similar to class but, it contains only abstract methods and fields which are final and static.Since Java8 static methods and default methods are introduced in interfaces. Unlike other abstract methods these are the methods can have a default implementation. If you have default method in an interface, it is not mandatory to override (provide body) it in the classes that are already implementing this interface.In short, you can access the default methods of an interface using the objects of the implementing classes.Exampleinterface MyInterface{ public static int num = 100; public default void ...
Read MoreHow to create the stacked bar plot using ggplot2 in R with labels on the plot?
The creation of stacked bar plot using ggplot2 can be done with the help of position="stack" argument inside geom_bar function. If we want to create the stacked bar plot then geom_text function will be used with the same position argument and the aes to define the labels as shown in the below example.Exampledf
Read MoreHow to find the extremes of a data frame column in R if infinity exists in the column?
To find the extremes of a data frame column that is numeric can be done with the help of min and max function but if we want to get the same in single line code then range function can be used. If there are some infinity values in the column then range.default function will be used as shown in the below example.Exampley1
Read MoreHow to check the least number of arguments a function expects in R?
To find the least number of arguments a function expects while using in R can be done with the help of the syntax: length(formals(“function_name”)). For example, to find the number of arguments expected by mutate function of dplyr package can be calculated by using the command length(formals(mutate)) but we need to make sure that the package is loaded.Exampleslibrary(ggplot2) length(formals(ggplot))Output[1] 4 length(formals(boxplot)) [1] 2 length(formals(qnorm)) [1] 5 length(formals(rnorm)) [1] 3 length(formals(rpois)) [1] 2 length(formals(runif)) [1] 3 length(formals(punif)) [1] 5 length(formals(plot)) [1] 3 length(formals(pbinom)) [1] 5 length(formals(qbinom)) [1] 5 length(formals(hist)) [1] 2 length(formals(data)) [1] 7 length(formals(matrix)) [1] 5 length(formals(list)) [1] 0 length(formals(data.frame)) ...
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