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How Can I Use Pointers in Java?

To know what a pointer is and what is the role of a pointer in Java, it’s important to know what a pointer is? The pointer can be described as the address of some location in memory. Pointers thus provide a direction to the link that we wish to reach out to. When studying Java, the role of pointers is played behind the curtain with a distinct name. Pointers in Java are often referred to as References in Java. When working with Java, the variable is a type of object that stores the reference of the object. And this reference is nothing but a pointer that provides the address of the object in the memory.

When an object variable is used in the program, the computer follows the pointer stored in the variable. The process is executed to search the actual object in the stack of memory. The address in the pointers in Java works as a road map to the variable and to reach the memory. The entire process occurs immediately and everything is left unseen as carried behind the scene. You do not have to worry about how the process is carried out or how the objects are referenced with the assistance of pointers.

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When we talk about C++, everything about the pointers in C++ becomes definitive. There are some special types of variables that can store the information as pointers. When you see a variable with a pointer, the computer will not directly follow the pointer and reach the variable; rather, you will have to command the computer to do so. To allow the computer to follow the pointer automatically, you will have to use a special notation to execute the effective working. 

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To create a new object for a pointer variable in Java, all you need to do is insert a “new” operator. The operator insertion is the same in C++ as well. In C++, you will have to take care that the command is removed from the places where the pointer is no longer needed. On the other hand, the pointer in Java is automatically disposed of without creating any notable unwanted variable. To dispose of the pointer command, you can use the operator “delete” in C++. All the exclusive working of the pointers is considered to be very tedious and prone to multiple errors and thus falls under the most advanced state of programming.

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Difference between Pointers in C++ and pointers in Java 

Let’s have a comprehensive look into the Pointers in C++ and Pointers in Java

  •  Pointers in C++ allow arithmetic but pointers in Java don’t: When we talk about “pointers”, it firmly talks about the one in C++, which are well-known variables for their ability to store memory addresses. Arithmetic modification of these variables is possible in C++ to point the arbitrary addresses.

The role of pointers in Java is only limited to implementation details of the References. A prototype of the reference is copied to the entire pile of called functions, which points towards the same object as that of the calling function. This also allows us to change and manipulate the object but cannot change the object referred to as the calling function.

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  • Pointers in Java are not used explicitly but have an implicit use: The use of pointers in Java is for the manipulation of the references. However,  these pointers are used for implicit functions and can’t be used for explicit purposes.

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  • Multiple pointing options in C++: In C or C++, it’s possible to add or deduct the addresses in the pointers to mark towards particular things. On the other hand, pointers in Java or references only point towards a single facet. It’s possible to make a variable hold a distinct reference, but such manipulation and alterations are not possible in C++.
  • Strong references in Java: C is quite lenient in terms of typing, while the same thing is not accepted in Java. The pointers in Java need a strong type than in C. In C language, you can use “int*” and cast it to a “char*” and just reinterpret the memory stored at that location. Such reinterpretation is not possible to execute in Java. You can only interpret that is already in and nothing else.
  • Manipulations in Pointers are not handy: it may seem flexible to implement the manipulations in pointers that can prove to be extremely dangerous if not used correctly. There are quite greater chances that the alterations made in the programming are incorrect and more prone to change the meaning of the function that you have fed in. Thus it’s crucial to understand that the use of manipulation in Pointers in Java can be hazardous and can result in adverse effects. 

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Thus as an outcome, the use of pointers is not as flexible in Java as in C++. The crucial reason is that the use of pointers in C++ is different when compared to the use of pointers in Java. The implementation of pointers in Java can make it more complex and robust, making it difficult to use but will add much greater security and robustness to the program.

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Comprehension about the Type of Pointers in C++ and pointers in Java  

Now let’s learn about the type used in pointers in Java and C++.

Any pointer in the C++ with the name of a specific type is implemented with an additional Asterix (*) sign after the command, this command represents the variable that holds the pointer of the object to type. While dealing with C++ the command can be added to any variable as the pointer of any type and not just limited to the object.

For instance, to rule the type of the variable on an integers command, the type used is “int*” and represents the pointers assigned to the integers in the programming. Such a type of variable will store the information and memory about an integer value stored at that location.

To add an actual pointer variable to the programming, you must add the variable “ptr” along with the type followed by the Asterix. Using the actual pointer implies you are using the type “ptr”, which is the memory address that is composed of the variable address. To refer to the value stored in the address contained in the pointer, use the type “*ptr”. C++ language makes use of predefined operators “NULL”, which indicates that the pointer is empty and doesn’t contain any information or address. To refer to a pointer with a nullified value is considered as an error.

Now let’s learn more about pointers in Java with the help of Java  Virtual Machine.

Java  Virtual Machine or as commonly known as JVM, is an engine to provide runtime for all Java codes and applications. Its role is to convert these codes into machine language for easy accessibility. 

We know that references in Java do not point memory and to retain the informational data, JVM is used to store the implementation, reference value, and its relatable access to the data. The JVM uses the implementation of references which are a combination of pointers mixed, where some of the bits are flags while some are the pointers pointing to some specific memory location.

Why are JVMs used instead of pointers?

The collection of garbage and cache at a place can alter the effectiveness of the programming. The use of JVM ensures effective cache and rubbish collection. In addition to preventing the fragmentation of memory, JVM moves the objects around in the memory. Once the memory used is done and objects are not referred any further, the catch memory is deleted. As the memory is freed, there is still a small fragment of memory that retains the information of the site visited under the huge stack of memory. 

We wish to ensure that the small fragment of this memory block should not split and remain as it is. What JVM does is that it stores all the relevant information related to the search in a new memory domain and continuously upgrades all the references to that object to keep an eye on track of the new location of the information.

Some Java  Garbage collections stop the use of other Java threads for a time and allow the upgrades to happen. This ensures that no Java code uses any non-upgraded data. The role of other Java  Garbage Collectors is to make sure that no external application threads can access the page and result in a fault.

The crucial thing to note is that the references are not the pointers in Java. 

How are pointers in Java used?

In Java, pointers are internally implemented to use in the complex data type lie arrays. While working and dealing with pointers in Java, you don’t need to get into the complete execution and internal implementation. All these facts are handled by the programming language. The language uses the pointers behind the scene and there is no need to add any specific system. Additionally, there are the least possible chances for the bugs to exist and affect the effectiveness of the program. The reason is that pointers in Java, like the NULL pointer, are productively exempted from the program.  

Also, there is one major difference in the pace of the working program. Java codes run slower than C language programming. The reason behind this is the reliability of the pointer on the user in C++.

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Benefits of using Pointers in Java 

Pointers in Java provide great support to the programmer to implement effective programming and search results. The major advantages of the pointers that make it a great hit among the users can be stated in the bulletins below. 

  • Management: The most vital role of the pointers is to manage the effective working of the program. Java is the language used in multiple domains today due to its high intended flexibility and easy-to-use capability. To add more to the programmer, management of the programming structure is what one seeks and pointers are the ones that provide explicit management of the allocated memory. Dynamic results are observed with the use of pointers in Java.
  • Passing arrays and strings: Array and string functions play a significant role in programming. The role of the pointers in Java is to allow the passing of strings and arrays and ensure more effective functioning of the commands. The entire programming includes a long lane if commanding array and strings and pointers raise the effectiveness of these arrays and strings.
  • Passing Address structure: Passing the entire structure of the program or data is critical. To ease out the chores, pointers assist in passing the addressing structure without extra toiling to pass the entire address structure to its relative functions.
  • Multiple functional Value: Functions are bound to deliver only single-valued outcomes. On the other hand, the use of pointers in Java will assist you in adding more than one value in return to a function with only a single value.

Pointers have aided the programmers to a great extent to enhance the effectiveness in the respective Java codes they use. Get in connection with the exact existence of the data uploaded on the web with the help of pointers. The use of Java codes can be a bit tricky, but the use of pointers can be beneficial to make the working simpler and flexible.

Understanding the Java Null Pointer

The Java null pointer is a runtime exception. It surfaces when the program attempts to use an object reference crucial for setting the null value. A code example to comprehend the Java null pointer is as follows:

class Main {
    public static void main(String[] args) {
        // Setting null value to the obj object
        Object obj = null;
        // Using object with null value
        System.out.println(obj.toString()); // It throws NullPointerException
    }
}

Output:

Exception in thread “main” java.lang.NullPointerException

        at Main.main(Main.java:8)

In the given code, the null value was initialized to an object obj. On the obj object, the toString() operation has been performed. Since the obj value is null, the null pointer exception is provided as the output. 

Function Pointers

Function pointers help indicate the address of a function. Some use cases of function pointers include developing a callback routine. A callback routine can be created with the help of a function calling another one based on its implementation. 

How to Simulate a Function Pointer

You will come across various method references for simulating a function pointer. Here, we will use the instance method of a specific object. 

The first step will look like this:

// Wrapping interface
private interface FunctionPointer {
  // Method signatures of pointed method
  void methodSignature(int a);
}

Next:

public void method1(int b) {
  System.out.println("Called method1 with integer " + b);
}
public void method2(int v) {
  System.out.println("Called method2 with integer " + v);
}
public void method3(int a) {
  System.out.println("Called method3 with integer " + a);
}
Next:
// Create a variable of the interface and assign

// the method references

FunctionPointer pointer1 = this::method1;

FunctionPointer pointer2 = this::method2;

// Call both methods using their "pointer"

pointer1.methodSignature(3);

pointer2.methodSignature(2);

// Reassign and call pointer 1

pointer1 = this::method3;

pointer1.methodSignature(5);

Output:
Called method1 with integer 3
Called method2 with integer 2
Called method3 with integer 5

Conclusion

Pointers in Java do not have an important role. You can define the other variables and use them accordingly. Java is said to be a complex and messy language as it does not have a fixed framework. If you are also confused about the concept, then you must try your hands on coding and generating results. Only practicing the language will make it simpler for you. 

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Frequently Asked Questions

What is the equivalent of C pointers in Java?

Pointers are a feature associated with the C programming language. They are responsible for providing the memory address in a situation where the programmer directly stores the data. But unfortunately, you won't find any pointers in Java. The closest thing to pointers are references in Java. A refers acts as a variable indicating something else and can be leveraged as an alias for the other thing. It's crucial to understand that every pointer is a reference. However, not all references are pointers.

What happens due to null pointer dereference in Java?

A null pointer dereference in Java takes place when an application tries to dereference or access a null object reference. Dereferencing a null pointer can contribute to sudden null pointer exceptions.

What are the primary benefits of using Java pointers?

Using pointers in Java can help with the easy management of structures that are provided with memory dynamically. It enables the passing of arrays and strings to function more efficiently. It also enables passing the address of the structure instead of the entire structure to the functions.

What are the two pointers primarily used for in Java?

The two-pointer approach is concerned with the index of an array. With the help of pointers, you will be able to process two elements of every loop instead of only one. One of the most popular two-pointer approach patterns includes the one where each pointer starts from the beginning and the end unless both pointers coincide.

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