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Programming Articles
Page 2383 of 2547
How do you check if a ResultSet is empty or not in JDBC?
Whenever we execute SQL statements using the executeQuery() method, it returns a ResultSet object which holds the tabular data returned by the SELECT queries(in general).The ResultSet object contains a cursor/pointer which points to the current row. Initially this cursor is positioned before first row (default position).The next() methodThe next() method of the ResultSet interface moves the pointer of the current (ResultSet) object to the next row, from the current position.This method returns a boolean value specifying whether the ResultSet object contains more rows. If there are no rows next to its current position this method returns false, else it returns true.Therefore, ...
Read MoreAccepting date strings (MM-dd-yyyy format) using Java regex?
The following is the regular expression to match the date in the dd-MM-yyyy format.^(1[0-2]|0[1-9])/(3[01]|[12][0-9]|0[1-9])/[0-9]{4}$To match a date in a string in that format.Compile the above expression of the compile() method of the Pattern class.Get the Matcher object bypassing the required input string as a parameter to the matcher() method of the Pattern class.The matches() method of the Matcher class returns true if a match occurs else it returns false. Therefore, invoke this method to validate the data.Example 1import java.util.regex.Matcher; import java.util.regex.Pattern; public class MatchingDate { public static void main(String[] args) { String date = "01/12/2019"; ...
Read MoreWhat is the use of the Tab key in JShell in Java 9?
JShell can also provide an auto-completion feature when we partially type the name of an existing class, variable, or method by pressing the Tab key. If an item can't determine from what we entered, then possible options are provided.Pressing the Tab key in JShell performs one of the following tasks:If no other name matches what we have typed, JShell enters the rest of the name for us.If there are multiple names that begin with the same letters, then JShell displays a list of those names to help what to type next, then type the next letter(s) and press tab key ...
Read MoreHow can we create an unmodifiable List in Java 9?
A list considered to be unmodifiable if the elements can't be added, removed, or replaced from a list once an unmodifiable instance of a list has created. The static factory method: List.of() provides a convenient way to create unmodifiable lists in Java 9.An instance of a list created by using the List.of() method has the following characteristics.The list returned by a factory method is conventionally immutable. It means that the elements can't be added, removed, or replaced from a list. Calling any mutator method on the List causes UnsupportedOperationException.If the contained elements of List are mutable, it may cause the ...
Read MoreImportance of iterate() method of Stream API in Java 9?
In Java 8, the iterate() method of Stream API takes the seed and the unary operator as arguments. As stream becomes infinite, it makes the developer add explicit termination conditions by using limit, findFirst, findAny and etc. In Java 9, the iterate() method of Stream API has added a new argument, a predicate that takes the condition to break the flow.Syntaxstatic Stream iterate(T seed, Predicate
Read MoreWhat does the method removeRange(int fromIndex, int toIndex) do in java?
The removeRange() method of the ArrayList class removes all of the elements from this List whose index is between fromIndex and toIndex.Exampleimport java.util.*; public class ArrayListDemo extends ArrayList{ public static void main(String[] args) { ArrayListDemo arrlist = new ArrayListDemo(); arrlist.add(10); arrlist.add(12); arrlist.add(31); System.out.println("The list:" + arrlist); arrlist.removeRange(0,2); System.out.println("The list after using removeRange:" + arrlist); } }OutputThe list:[10, 12, 31] The list after using removeRange:[31]
Read MoreWhat does the method set(int, obj o) do in java?
The set() method of the ArrayList class replaces the element at the specified position in this list with the specified element.Exampleimport java.util.ArrayList; public class Sample { public static void main(String args[]) { ArrayList al = new ArrayList(); System.out.println("Initial size of al: " + al.size()); al.add("C"); al.add("A"); al.add("E"); al.add(1, "A2"); System.out.println("Size of al after additions: " + al.size()); System.out.println("Contents of al: " + al); System.out.println("Size of al after deletions: " + al.size()); ...
Read MoreWhat does the method indexOf(obj o) do in java?
The indexOf(Object) method of the java.util.ArrayList class returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.Exampleimport java.util.ArrayList; public class ArrayListDemo { public static void main(String[] args) { ArrayList arrlist = new ArrayList(5); arrlist.add("G"); arrlist.add("E"); arrlist.add("F"); arrlist.add("M"); System.out.println("Size of list: " + arrlist.size()); for (String value : arrlist) { System.out.println("Value = " + value); } ...
Read MoreWhat does the method size() do in java?
The size() method of the class java.util.ArrayList returns the number of elements in this list i.e. the size of the list.Exampleimport java.util.ArrayList; public class ArrayListDemo { public static void main(String[] args) { ArrayList arrlist = new ArrayList(5); arrlist.add(15); arrlist.add(20); arrlist.add(25); arrlist.add(22); for (Integer number : arrlist) { System.out.println("Number = " + number); } int retval = arrlist.size(); System.out.println("Size of list = " + retval); } }OutputNumber = 15 Number = 20 Number = 25 Number = 22 Size of list = 4
Read MoreWhat does the method remove(obj o) do in java?
The remove(Object) method of the class java.util.ArrayList removes the first occurrence of the specified element from this list, if it is present. If the list does not contain the element, it is unchanged.Exampleimport java.util.ArrayList; public class ArrayListDemo { public static void main(String[] args) { ArrayList arrlist = new ArrayList(5); arrlist.add("G"); arrlist.add("E"); arrlist.add("F"); arrlist.add("M"); arrlist.add("E"); System.out.println("Size of list: " + arrlist.size()); for (String value : arrlist) { System.out.println("Value = " + ...
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