An array in java is a container that can hold fixed number of values of same type. The values can be of primitive type like int, short, byte or it can be an object like String, Integer etc.rnHow to initialize an Array in JavarnAn array can be one dimensional or it can be multidimensional also. When we invoke length of an array, it returns the number of rows in array or the value of left most dimension.rnWe can initialize array using new keyword or using shortcut syntax which creates and initialize array at the same time.rnWhen we create an array using new operator, we need to provide it’s dimensions. For multidimensional arrays, we can provide all the dimensions or only the left most dimension of the array.rnNormally, array is a collection of similar type of elements that have contiguous memory location.rnJava array is an object the contains elements of similar data type. It is a data structure where we store similar elements. We can store only fixed set of elements in a java array.rnArray in java is index based, first element of the array is stored at 0 index.rnAdvantage of Java Arrayrn• Code Optimization: It makes the code optimized, we can retrieve or sort the data easily.
• Random access: We can get any data located at any index position.
Disadvantage of Java Arrayrn• Size Limit: We can store only fixed size of elements in the array. It doesn't grow its size at runtime. To solve this problem, collection framework is used in java.rnTypes of Array in javarnThere are two types of array.
• Single Dimensional Arrayrn• Multidimensional ArrayrnTwo Dimensional Array in JavarnSo we can define a two dimensional array of primitive data types as well as objects.rnJava Array of ArrayListrnNotice that we can’t use generics while creating the array because java doesn’t support generic array. it will produce compile time error as “Cannot create a generic array of List”.rnJava ArrayList of Object ArrayrnIf you are not sure about the type of objects in the array or you want to create an arraylist of arrays that can hold multiple types, then you can crate an ArrayList of object array.rnJava varargsrnJava varargs was introduced in Java 1.5. Java varargs is also known as java variable arguments.rnJava varargsrnvarargs in java enables a method to accept variable number of arguments. We use three dots (…) also known as ellipsis in the method signature to make it accept variable arguments.rnImportant points about varargs in javarnFew points to know about varargs in java are;rn1. We can have only one varargs in the method.rn2. Only the last argument of a method can be varargs.rn3. According to java documentation, we should not overload a varargs method. We will see why it’s not a good idea.rnHow java varargs work?rnWhen we invoke a method with variable arguments, java compiler matches the arguments from left to right. Once it reaches to the last varargs parameter, it creates an array of the remaining arguments and pass it to the method. In fact varargs parameter behaves like an array of the specified type.rnJava String to String Array ExamplernSometimes we need to split String to String arrays based on delimiters or some regular expression. For example, reading a CSV file line and parsing them to get all the data to String array.rnString class split(String regex) can be used to convert String to String array in java, if you are working with java regular expression, you can use Pattern class split(String regex) method also.rnJava Array add elementsrnHow to add elements to an array in java? We know that java array add elements is not supported because size of an Array in java is fixed. We have to provide size of the array when we initialize array in java.rnHow to sort an Array in JavarnJava Array is like a container that can hold fixed number of same type of items, it can be primitive types as well as Objects.rnSometimes we need to sort array in java, we will use Arrays class to sort the array.
Java String Array to String
Java String array to String. Sometimes we have to convert String array to String for specific requirements. For example; we want to log the array contents or we need to convert values of String array to String and invoke other methods.rnJava String Array to StringrnMost of the time we invoke toString() method of an Object to get the String representation. Let’s see what happens when we invoke toString() method on String array in java.rnSo how to convert String array to String in java. We can use Arrays.toString method that invoke the toString() method on individual elements and use StringBuilder to create String.rnWe can also create our own method to convert String array to String if we have some specific format requirements.