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Detail Description About Java Arrays
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How to initialize an Array in Java
An 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.
We can initialize array using new keyword or using shortcut syntax which creates and initialize array at the same time.
When 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.
Normally, array is a collection of similar type of elements that have contiguous memory location.
Java 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.
Array in java is index based, first element of the array is stored at 0 index.
Advantage of Java Array
• 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 Array
• 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.
Types of Array in java
There are two types of array.
• Single Dimensional Array
• Multidimensional Array
Two Dimensional Array in Java
So we can define a two dimensional array of primitive data types as well as objects.
Java Array of ArrayList
Notice 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”.
Java ArrayList of Object Array
If 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.
Java varargs was introduced in Java 1.5. Java varargs is also known as java variable arguments.
varargs 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.
Important points about varargs in java
Few points to know about varargs in java are;
1. We can have only one varargs in the method.
2. Only the last argument of a method can be varargs.
3. According to java documentation, we should not overload a varargs method. We will see why it’s not a good idea.
How java varargs work?
When 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.
Java String to String Array Example
Sometimes 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.
String 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.
Java Array add elements
How 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.
How to sort an Array in Java
Java Array is like a container that can hold fixed number of same type of items, it can be primitive types as well as Objects.
Sometimes 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.
Java String Array to String
Most 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.
So 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.
We can also create our own method to convert String array to String if we have some specific format requirements.
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