What is a Wrapper Class in Java?
Java is an object-oriented language that converts a primitive data type into a class object; hence, wrapper class objects enable us to convert the original passed value. These wrapper classes support the multithreading and synchronisation process. With the help of this, we can work with collections like Vector, LinkedList, ArrayList.
Java programming language offers java.lang package that includes the Object and Class. Along with the above overview on what is wrapper class in java, you must know what they represent. Java wrapper classes represent or wrap the primitive data types’ values as an object. When an object is defined in a wrapper class, it includes a field that can store the primitive data types’ values.
Note that the object of one data type includes a field of the specific data type only. So, an object’s double type contains the double type of the field only. It represents that value to store the corresponding reference in a reference type’s variable.
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When a wrapper class object is created, the space is allocated in the memory. This is where the primitive data type is saved. Moreover, the wrapper class supports some functionalities for transforming the object into primitive data and, eventually, primitive data into the object. These conversion processes happen automatically. After we understand what is wrapper class in java, let’s go through the process flow of the wrapper class.
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Process Flow of the Wrapper Class
In a wrapper class, we create the object with fields or properties, where we can use and store the primitive data types.
Java implements in-built classes corresponding to specific primitive types that can be applied to modify these value types in object types. We can consider and identify these inbuilt classes as wrapper classes or primitive wrapper classes.
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Use of Wrapper Class in Java Programming
- We can use the wrapper class and create a function with parameters using primitive data types.
- We can change the primitive data type into a distinct wrapper class.
- Wrapper class allows various methods while using collections like sorting and searching.
- The wrapper class implements the technique to convert the primitive into object and object into primitive.
- There is a concept of autoboxing and unboxing in the wrapper class, which transform the primitives into objects and objects into primitives automatically.
- In Java, we have a synchronisation mechanism that works with objects in multithreading.
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Need for using Wrapper Classes in Java:
To understand how wrapper classes are helpful in Java, you should be clear about what are wrapper classes in java. The wrapper classes in java can be used when it is required to use the primitive types as objects. Moreover, wrapper classes also contain methods that unwrap the object and return the data type.
- The classes only handle objects in java.util package. In this case, the wrapper class proves to be useful.
- Data Structures like ArrayList only store the objects, not the primitive types in the Collection framework.
- The wrapper classes in java are used for the methods that support objects like a conversion from other types.
- Wrapper classes are useful for synchronization in multithreading. The synchronization process allows only one thread to use a shared resource at a time. For that, wrapper class objects are required.
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What are Primitive Data Types?
After being familiar with what are wrapper classes in java and their usefulness, it’s important to learn about the primitive data types. Before going into a deeper understanding of the wrapper class object, we need to understand the concept of primitive data types:
A primitive data type defines the size and type of variable values. In Java, we have eight primitive data types, which are as follows:
Primitive Data Types are the basic building blocks of data manipulation in Java. Knowing Primitive Data Types helps you understand the wrapper classes better.
Java is a statically-typed programming language, so any variable can’t be used without declaration. So, data types are used for variable declaration. Fundamentally, the data type is the type of variable that defines the value it may include and the operations that can be performed on it.
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Primitive data types come with a limitation, i.e., they can contain data of the same type, and the size is fixed based on the data type. For instance, 1 byte can only store whole numbers ranging from -128 to 127. Moreover, the primitive data types always hold a value
Features of Java Wrapper Classes
- Wrapper classes transmute numeric strings into numeric values.
- We can store primitive data into an object.
- We can use the valueOf() method in all the wrapper classes without string.
- We can use the typeValue() for all the available wrapper classes. It performs as the primitive type and returns the value of the object.
Below are the Features of the Wrapper Class:
- Modification of the value in function: In java programming, we have the ‘call by value’ function, with the help of which we can pass the primitive value parameter. In many cases, the argument needs to be modified so that we can pass the objects and accordingly modify the values.
- Serialisation: In serialisation, we convert the object within streams to implement the serialisation. We can regenerate it in the object with the help of the classes of the wrapper. Objects are inevitable because the Serializable interface should be implemented by the class whose object is persevered.
- Synchronisation: Java synchronisation operates into objects in multi-threading.
- java.util package: The java.util package implements the utility classes to match with objects.
- Collection framework: Java collection framework operates including objects only. Here, we have many collection framework classes—for example—HashSet, TreeSet, ArrayDeque, ArrayList, Vector, and LinkedList. All these collection framework classes only store objects, i.e., reference types, and not the primitive types. Hence, objects are wrapper classes’ instances, and therefore, they are helpful for this.
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Methods Supported by the Wrapper Classes
If you aim to thoroughly learn what is wrapper class, you must learn the supported methods described below:
Some of the commonly used methods implemented by all subclasses of the Number class are described here:
typeValue() -Converts the value of the particular Number object to the stated primitive data type returned
compareTo() – Compares the Number object with the argument
equals() – Checks whether the Number object equals the argument
valueOf() – Returns an Integer object containing the specified primitive data type’s value
toString() – Returns a String object containing the specified Integer type argument’s value
parseInt() – Returns an Integer type value of a stated String representation
decode() – Decodes a String into an integer
min() – Compares the two arguments and returns the smaller value
max() – Compares the two arguments and returns the bigger value
round() – Returns the closest round off of int or long value according to the method return type
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Use of Autoboxing and Unboxing in Wrapper Class with Examples
Autoboxing: It is the automated transformation of primitive types to the object of their corresponding wrapper classes—for example, conversion of long to Long and int to Integer, double to Double.
The Java compiler implements autoboxing when a primitive value is:
- Passed as a parameter to a method that requires an object of the equivalent wrapper class
- Assigned to the equivalent wrapper classes’ variable
Unboxing in Java
Unboxing is the reverse of Autoboxing. It is the method of converting a Wrapper class object within its corresponding Primitive Data type. For example, we can convert an Integer object into a primitive data type, as int.
The Java compiler implements unboxing when a wrapper class’ object is:
- Assigned to the corresponding primitive type’s variable
- Passed as a parameter to a method that requires the corresponding primitive type’s value
Need for Autoboxing and Unboxing in Java:
- The addition of autoboxing and unboxing greatly simplifies the coding of many algorithms. They eliminate the need for manually boxing and unboxing the values.
- It helps avoid errors.
- It is quite significant to generics that execute only on objects.
Benefits of Wrapper Classes
- Wrapper class provides various methods which we can use with collections like sorting, searching.
- We can use the objects of the wrapper class and store them as a null value.
- A wrapper type allows a primitive to operate in more advanced ways. An integer can use it in different ways, like a class described as Hours, for example, which presents the number meaning wherever it is used.
- The primitive types just operate value; the wrapper class provides it with a name.
- Wrapper objects are natural objects, and their references can be null. This enables the usage of a ‘not set’ state, which is difficult with primitives.
- Objects like Integer and Character are pointers. The variable’s value in bytes shows an address in the memory. They are the references to the memory address. Hence, it is possible to set that number to an address that directs to nowhere.
- A primitive data type like char or int contains a number that is interpreted as a number only (ASCII code or integer). Since the memory can only store numbers, there is no alternative to making it ‘not a number’.
- A wrapper class allows a primitive data type to work in various innovative ways. An integer can use this data type in various ways. For example, a class ‘Hours’ will always represent the number wherever it is used.
- The primitive types only run with the value, whereas the wrapper class provides a name. For example, int as Integer means only int specifies the value’s type and range. However, by creating the object with the wrapper class ‘Integer’, it will be provided a reference name(object).
- All the numeric wrapper classes are subclasses of the abstract class “Number” including Integer, Byte, Short, Double, Long, and Float.
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We hope this article helped you with the understanding of the wrapper class in Java.
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What are wrapper classes in Java?
In the Java language, a wrapper class is an interface which is used to pass a primitive type to the object-oriented component. For example, if we want to pass int value to the object class then we have to create a wrapper class which is written like Integer and after that we can use this wrapper class as an object and pass integer values to the object class and can do manipulations on primitive values. In Java, a wrapper class is a class that wraps one or more primitive data types. Wrapper classes are very common in java. For example, String, Integer and Boolean are wrapper classes. Wrapper classes are used to treat primitive data types as objects.
What are the advantages of wrapper classes in Java?
With wrapper classes, developers get the best of both worlds. Developers can use primitive values directly from the wrapper, or access the corresponding wrapper object methods. This means you can use the wrapper class to represent a primitive value (like a float) but the float is automatically created, read and written like a normal wrapper object (like a Double). This is much safer than storing primitives in a wrapper.
What is autoboxing and unboxing in Java?
Autoboxing and unboxing refers to situations where primitive values are automatically wrapped into their corresponding wrapper classes. Suppose if you have a value 5 and you assign that value to a variable of type Integer, the compiler will automatically box that value and will create a wrapper instance. This wrapper instance is an Integer class, rather than an int. Similarly, if you assign this Integer wrapper to a variable of type Double, the compiler will automatically unbox it, and it will wrap the value 5 into a primitive value of type double, and assign it to the variable of type double. Unboxing works in a similar manner. Suppose, you have a reference of an Integer class, which is an object, and you assign that object to a variable of primitive type int, the compiler will actually unbox the object and create a primitive int object. This is called primitive unboxing.