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Page 305 of 589
How 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 ...
Read MoreHow to extract an HTML tag from a String using regex in Java?
In this article, we will see how to extract an HTML tag from a string using regex in Java. We can achieve this in multiple ways, but if we use regex, it will be better than others and also give us fast performance. What is Regex? Regex is a sequence of characters that describes a search pattern that is used to find a particular pattern in a String. It is also known as a regular expression or regexp. We use regex for pattern matching or searching or replacing a String. We will use the java.util.regex package of Java that provides ...
Read MoreHow convert an array of Strings in a single String in java?
In this article, we will learn how to convert an array of strings into a single string in Java. There are several ways to do so. The following are the different ways to convert an array of strings into a single string: Using the StringBuffer class. Using the toString() method of the Arrays class. Using the StringJoiner class. Using StringBuffer The StringBuffer class is used for creating mutable (modifiable) strings. It is similar to the String class, but it is mutable. The StringBuffer class is synchronized, which means it is thread-safe. To convert an array of strings into ...
Read MoreHow can we add an underscore before each capital letter inside a java String?
In this article, we will learn how to add an underscore before each capital letter in a Java String. We also call this process as "camel case to snake case" conversion. We can solve this problem using the following ways: Using StringBuffer class. Using Regular Expressions. Using StringBuffer class We will use the method called append() of the StringBuffer class to add an underscore. In this method, we will traverse through each character of the string and check if it is an uppercase letter. If it is, we will append ...
Read MoreWhat are the rules of exception handling with respect to method overriding in java?
While a superclass method throws an exception when overriding it, you need to follow certain rules. We will be discussing these rules in this chapter. What is Exception Handling in Java? Exception handling is a mechanism to handle errors in the program. For example, if a program tries to divide a number by zero, it will throw an ArithmeticException. In such cases, the program will terminate abnormally. To avoid this, we can use exception handling. Now, let's discuss the rules of exception handling with respect to method overriding. Those are: Should throw the same exception or a subtype ...
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