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Object Oriented Programming Articles
Page 147 of 588
How can we ignore the fields during JSON serialization in Java?
If there are fields in Java objects that do not wish to be serialized, we can use the @JsonIgnore annotation in the Jackson library. The @JsonIgnore can be used at the field level, for ignoring fields during the serialization and deserialization. In this article, we will learn how to ignore the fields during JSON serialization in Java using the Jackson library. Steps to ignore the fields during JSON serialization in Java: In order to use Jackson, you will need to add it to your project. If you use Maven, add the following dependency to your ...
Read MoreDifferences between Method Reference and Constructor Reference in Java?
The Method Reference and Constructor Reference are part of Java 8's functional programming features, they used for refering to methods and constructors without executing them. They are often used in conjunction with functional interfaces, such as those defined in the java.util.function package. Method Reference A method reference is a shorthand representation of a lambda expression for calling a method. A method reference refers to a method without executing it. Method references can refer to static methods, instance methods, and constructors. Constructor Reference A constructor reference is a unique kind of method reference that is a reference to a constructor. ...
Read MoreConstructor Chaining In Java programming
The constructor chaining is a specific sequence of calling constructors when a user initializes an object in a certain way. This technique is used when multiple constructors are invoked one after another, based on the instance class. It is also closely related to inheritance, where the role of a subclass constructor is to call the constructor of its superclass. You can perform constructor chaining in two ways: Within the same class - where one constructor calls another constructor of the same class. Across different classes - where a subclass constructor calls ...
Read MoreWhy an interface doesn\\\\\'t have a constructor whereas an abstract class have a constructor in Java?
Interfaces in Java are used for defining a contract that classes can implement. They can contain method signatures, default methods, static methods, and constants. we must implement the methods defined in the interface in the implementing class. Constructor in an Interface A Constructor is to initialize the non-static members of a particular class with respect to an object. An Interface in Java doesn't have a constructor because all data members in interfaces are public static final by default, they are constants (assign the values at the time of declaration). There are ...
Read MoreHow do we check if a String contains a substring (ignoring case) in Java?
Problem Statement The task is, given a string and a substring, you have to check if a substring is present in a string or not. Do not mind if the case of the string and substring is different, it should not matter. For example, if the string is "Hello World" and the substring is "hello", then the output should be true. Even if the substring is "HELLO" or "HeLLo", the output should be true. Solution To solve this problem, we will first convert the string and the substring to lowercase using the toLowerCase() method. The toLowerCase () method of the ...
Read MoreSorting contents of a string that holds integer values in Java
Problem Statement Here we have a string that contains integer values, our task is to sort those integer values in ascending order. For example, if the string is "31134", the sorted string should be "11334". Solution We can solve the above problem using multiple ways: Using char array Using Stream API Using Bubble Sort Using char array We will use the toCharArray() method of the String class to convert the string into a character array. Then we will sort the character array using the Arrays.sort() method. ...
Read MoreHow to get first and last elements from ArrayList in Java?
ArrayList is a part of the Java Collections Framework. Which is a dynamic type of array that can grow and shrink as needed. It is a resizable array implementation of the List interface. The ArrayList class is used when we want to store a list of elements in a dynamic array. In this article, let's learn how to get the first and last elements from an ArrayList in Java. The get() method of the ArrayList class accepts an integer representing the index value and returns the element of the current ArrayList object at the specified index. Therefore, if you pass ...
Read MoreHow can a String be validated (for alphabets) in java?
Problem Statement The given problem is to validate a string to check if that string contains only alphabets (both uppercase and lowercase) and does not contains any other characters like numbers, special characters, etc.. For example, the string "HelloWorld" is valid as it contains only alphabets, while "Hello123" is not valid as it contains numbers. Solution We can solve this problem by using following methods: Using Regular Expressions Manual Checking using loop Using Character.isAlphabetic() Using Regular Expressions We can use regular expressions to validate a string for alphabets. The regular expression ^[a-zA-Z]+$ matches a string that contains only ...
Read MoreHow to create a variable that can be set only once but isn\\\'t final in Java?
How to create a variable that can be set only once, meaning it can be assigned a value only once but is not final in Java? Solution In Java we can solve the above using the following two methods: Using a custom wrapper class Using an AtomicReference Using a custom wrapper class We can create a custom wrapper class that allows setting a value only once. The class will have a boolean flag to check if the value has already been set. Wrapper classes are used for converting primitive data types into objects. We will use this for setting ...
Read MoreHow to Convert a String to Hexadecimal and vice versa format in java?
In this article, we will learn how to convert a string to hexadecimal and hexadecimal to string in Java. Hexadecimal is a base-16 number system that uses 16 symbols to represent a number. Those symbols can be 0-9 and A-F letters. String to Hexadecimal in Java To convert a string to hexadecimal in Java, we can use the toHexString() method of the Integer class accepts an integer as a parameter and returns a hexadecimal string. Following are the steps to convert a string to hexadecimal: Get the desired String. Create an empty StringBuffer object. Convert it into a ...
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