Use $addToSet to create a new field in MongoDB. Let us first create a collection with documents −> db.createFieldDemo.insertOne({"StudentFirstName":"John", "StudentAge":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd99e28b50a6c6dd317ad95") } > db.createFieldDemo.insertOne({"StudentFirstName":"Larry", "StudentAge":23}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd99e2fb50a6c6dd317ad96") } > db.createFieldDemo.insertOne({"StudentFirstName":"Chris", "StudentAge":22}); {    "acknowledged" : ... Read More

To automatically resize a JTree, use the setVisibleRowCount() method in Java. At first, create a node in the tree −DefaultMutableTreeNode node = new DefaultMutableTreeNode("Project");Now, add nodes to the node created above −DefaultMutableTreeNode node1 = new DefaultMutableTreeNode("App"); DefaultMutableTreeNode node2 = new DefaultMutableTreeNode("Website"); DefaultMutableTreeNode node3 = new DefaultMutableTreeNode("WebApp"); node.add(node1); node.add(node2); node.add(node3);Now, create ... Read More

Here we will see some incompatibilities between C and C++. Some C codes that can be compiled using C compiler, but does not compile in C++ compiler. And also returns error.We can define function using a syntax, that optionally specify the argument types after the argument list.Example#include void my_function(x, y)int ... Read More

Let us first create a table with rows and columns −String data[][] = { {"Australia", "5", "1"},    {"US", "10", "2"},    {"Canada", "9", "3"},    {"India", "7", "4"},    {"Poland", "2", "5"},    {"SriLanka", "5", "6"} }; String col [] = {"Team", "Selected Players", "Rank"}; DefaultTableModel tableModel = new ... Read More

To get particular field as a result in MongoDB, you can use findOne(). Following is the syntax −db.yourCollectionName.findOne({"yourFieldName1":yourValue}, {yourFieldName2:1});Let us first create a collection with documents −> db.particularFieldDemo.insertOne({"EmployeeName":"John Smith", "EmployeeAge":26, "EmployeeTechnology":"MongoDB"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd9b4abb50a6c6dd317ada2") } > db.particularFieldDemo.insertOne({"EmployeeName":"Chris Brown", "EmployeeAge":28, "EmployeeTechnology":"Java"}); {    "acknowledged" : ... Read More

Contigous selection means sharing borders like selecting siblings of a node in a JTree. To allow contiguous selection of nodes, set the selection mode to CONTIGUOUS_TREE_SELECTION −tree.getSelectionModel().setSelectionMode(TreeSelectionModel.CONTIGUOUS_TREE_SELECTION);The following is an example to allow contigous selection of nodes in a JTree −Examplepackage my; import javax.swing.JFrame; import javax.swing.JTree; import javax.swing.tree.DefaultMutableTreeNode; import javax.swing.tree.TreeSelectionModel; public class SwingDemo {    public static void main(String[] args) throws Exception {     ... Read More

In C we have used Files. To handle files, we use the pointer of type FILE. So the FILE is a datatype. This is called the Opaque datatype. So its implementation is hidden. The definition of the FILE is system specific. This is the definition of FILE in Ubuntu System ... Read More

Use delete operator to unset variable in MongoDB shell. Following is the syntax −delete yourVariableName;Let us now implement the above syntax in order to unset variable in MongoDB shell. First, print the variable name −> customerDetail;This will produce the following output −2019-05-08T22:29:17.361+0530 E QUERY [js] ReferenceError: customerDetail is not defined ... Read More

You can use $gt operator for this. Let us first create a collection with documents −> db.arrayElementsNotGreaterThanDemo.insertOne({"Scores":[89, 43, 32, 45]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd9e9f9b50a6c6dd317adb3") } > db.arrayElementsNotGreaterThanDemo.insertOne({"Scores":[32, 33, 34, 40]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cd9ea13b50a6c6dd317adb4") } > db.arrayElementsNotGreaterThanDemo.insertOne({"Scores":[45, 56, 66, 69]}); ... Read More

Here we will see what is the use of ldexp() method in C or C++. This function returns any variable x raise to the power of exp value. This takes two arguments x and exp.The syntax is like below.float ldexp (float x, int exp) double ldexp (double x, int exp) ... Read More