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Our Advanced Java Interview Questions- Part 2 is your ultimate guide to clearing advanced Java interviews with confidence. Java has remained one of the world’s top four programming languages for over 20 years, according to the TIOBE Index.
While many new languages have tried to replace it, Java is still widely used and in demand, even in 2025. A quick search for “Java” jobs in the U.S. will show thousands of openings. But before applying, it’s important to prepare for Java interview questions.
Top skills like Spring Boot, microservices, and cloud computing (AWS, Azure) are essential for building scalable, modern apps. Our interview questions with answers, perfect, will help you master tough concepts like multithreading, REST APIs, and JVM. Start learning now to stand out in interviews and land a high-paying Java job.
[/fusion_text][/fusion_builder_column][/fusion_builder_row][/fusion_builder_container][fusion_builder_container type=”flex” hundred_percent=”no” hundred_percent_height=”no” min_height=”” hundred_percent_height_scroll=”no” align_content=”stretch” flex_align_items=”flex-start” flex_justify_content=”flex-start” flex_column_spacing=”” hundred_percent_height_center_content=”yes” equal_height_columns=”no” container_tag=”div” menu_anchor=”” hide_on_mobile=”small-visibility,medium-visibility,large-visibility” status=”published” publish_date=”” class=”” id=”” margin_top_medium=”” margin_bottom_medium=”” margin_top_small=”” margin_bottom_small=”” margin_top=”” margin_bottom=”” padding_top_medium=”” padding_right_medium=”” padding_bottom_medium=”” padding_left_medium=”” padding_top_small=”” padding_right_small=”” padding_bottom_small=”” padding_left_small=”” padding_top=”” padding_right=”” padding_bottom=”” padding_left=”” link_color=”” link_hover_color=”” border_sizes_top=”10px” border_sizes_right=”10px” border_sizes_bottom=”10px” border_sizes_left=”10px” border_color=”#007dc6″ border_style=”solid” box_shadow=”yes” box_shadow_vertical=”4″ box_shadow_horizontal=”4″ box_shadow_blur=”30″ box_shadow_spread=”0″ box_shadow_color=”rgba(0,0,0,0.32)” box_shadow_style=”” z_index=”” overflow=”” gradient_start_color=”” gradient_end_color=”” gradient_start_position=”0″ gradient_end_position=”100″ gradient_type=”linear” radial_direction=”center center” linear_angle=”180″ background_color=”” background_image=”” background_position=”center center” background_repeat=”no-repeat” fade=”no” background_parallax=”none” enable_mobile=”no” parallax_speed=”0.3″ background_blend_mode=”none” video_mp4=”” video_webm=”” video_ogv=”” video_url=”” video_aspect_ratio=”16:9″ video_loop=”yes” video_mute=”yes” video_preview_image=”” render_logics=”” absolute=”off” absolute_devices=”small,medium,large” sticky=”off” sticky_devices=”small-visibility,medium-visibility,large-visibility” sticky_background_color=”” sticky_height=”” sticky_offset=”” sticky_transition_offset=”0″ scroll_offset=”0″ animation_type=”” animation_direction=”left” animation_speed=”0.3″ animation_offset=”” filter_hue=”0″ filter_saturation=”100″ filter_brightness=”100″ filter_contrast=”100″ filter_invert=”0″ filter_sepia=”0″ filter_opacity=”100″ filter_blur=”0″ filter_hue_hover=”0″ filter_saturation_hover=”100″ filter_brightness_hover=”100″ filter_contrast_hover=”100″ filter_invert_hover=”0″ filter_sepia_hover=”0″ filter_opacity_hover=”100″ filter_blur_hover=”0″][fusion_builder_row][fusion_builder_column type=”1_1″ layout=”1_1″ align_self=”auto” content_layout=”column” align_content=”flex-start” valign_content=”flex-start” content_wrap=”wrap” spacing=”” center_content=”no” link=”” target=”_self” min_height=”” hide_on_mobile=”small-visibility,medium-visibility,large-visibility” sticky_display=”normal,sticky” class=”” id=”” background_image_id=”” type_medium=”” type_small=”” order_medium=”0″ order_small=”0″ spacing_left_medium=”” spacing_right_medium=”” spacing_left_small=”” spacing_right_small=”” spacing_left=”” spacing_right=”” margin_top_medium=”” margin_bottom_medium=”” margin_top_small=”” margin_bottom_small=”” margin_top=”” margin_bottom=”” padding_top_medium=”” padding_right_medium=”” padding_bottom_medium=”” padding_left_medium=”” padding_top_small=”” padding_right_small=”” padding_bottom_small=”” padding_left_small=”” padding_top=”20px” padding_right=”20px” padding_bottom=”20px” padding_left=”20px” hover_type=”none” border_sizes_top=”” border_sizes_right=”” border_sizes_bottom=”” border_sizes_left=”” border_color=”” border_style=”solid” border_radius_top_left=”” border_radius_top_right=”” border_radius_bottom_right=”” border_radius_bottom_left=”” box_shadow=”no” box_shadow_vertical=”” box_shadow_horizontal=”” box_shadow_blur=”0″ box_shadow_spread=”0″ box_shadow_color=”” box_shadow_style=”” background_type=”single” gradient_start_color=”” gradient_end_color=”” gradient_start_position=”0″ gradient_end_position=”100″ gradient_type=”linear” radial_direction=”center center” linear_angle=”180″ background_color=”” background_image=”” background_position=”left top” background_repeat=”no-repeat” background_blend_mode=”none” render_logics=”” filter_type=”regular” filter_hue=”0″ filter_saturation=”100″ filter_brightness=”100″ filter_contrast=”100″ filter_invert=”0″ filter_sepia=”0″ filter_opacity=”100″ filter_blur=”0″ filter_hue_hover=”0″ filter_saturation_hover=”100″ filter_brightness_hover=”100″ filter_contrast_hover=”100″ filter_invert_hover=”0″ filter_sepia_hover=”0″ filter_opacity_hover=”100″ filter_blur_hover=”0″ animation_type=”” animation_direction=”left” animation_speed=”0.3″ animation_offset=”” last=”true” border_position=”all” first=”true”][fusion_accordion type=”accordions” boxed_mode=”no” border_size=”1″ border_color=”” background_color=”” hover_color=”” divider_line=”” title_font_size=”” icon_size=”” icon_color=”” icon_boxed_mode=”” icon_box_color=”#4f4f4f” icon_alignment=”right” toggle_hover_accent_color=”#3ed9df” hide_on_mobile=”small-visibility,medium-visibility,large-visibility” class=”interview_list” id=””][fusion_toggle title=”Question 21: How to serialize an object to a file?” open=”no” class=”” id=””]
Answer:
To serialize a class instance, you need to implement an interface serializable & then pass the instance to the ObjectOutputStream connected to a FileOutputStream. Thus, it will save the object to a file.
[/fusion_toggle][fusion_toggle title=”Question 22 : Which methods of Serializable interface should you implement?” open=”no” class=”” id=””]
Answer:
The Serializable interface is also a marker interface that does not have any methods & fields. Thus, a class implementing Serializable does not have to implement any methods.
[/fusion_toggle][fusion_toggle title=”Question 23 : What happens to object references included in the ssobject when you serialize an object?” open=”no” class=”” id=””]
Answer:
Serialization generates an object graph for serialization. It checks if the included object references are serializable or not. It is a recursive process; means if an object is serialized, all the included objects also get serialized along with that object.
[/fusion_toggle][fusion_toggle title=”Question 24 : What happens to a class’s static variables during serialization?” open=”no” class=”” id=””]
Answer:
Static variables do not belong to any individual instance; instead, they belong to an object. Besides, serialization only regards the object’s current state, so only data associated with a class’s specific instance gets serialized. Thus, the static member fields are usually ignored during serialization.
[/fusion_toggle][fusion_toggle title=”Question 25 : How does an exception permeate through a code?” open=”no” class=”” id=””]
Answer:
When an exception is thrown from the code wrapped in a try block, a search is made to match a catch block. If it finds a matching type, then that block is invoked. However, if it fails to find a matching type, the exception moves up the method stack & reaches the caller method.
[/fusion_toggle][fusion_toggle title=”Question 26 : How to use the Observer & Observable?” open=”no” class=”” id=””]
Answer:
Java Observer pattern is used in the design. When the state of an observable object changes, its corresponding observer classes get notified. An Observable implement as a class that includes methods to manage Observers list & notifying Observers.
[/fusion_toggle][fusion_toggle title=”Question 27 : How does Java deal with integer overflows & underflows?” open=”no” class=”” id=””]
Answer:
Java does not handle or deal with integer overflows & underflows. The values are wrapped around by adding one to the maximum values of a primitive data type that returns the minimum value.
[/fusion_toggle][fusion_toggle title=”Question 28 : Mention the difference between Exception & Error?” open=”no” class=”” id=””]
Answer:
Below are the key differences between Exceptions & Errors:
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| Errors | Exceptions |
|---|---|
| Errors are raised by the environment when the application is running. For instance, an error will occur due to fewer system resources. | Exceptions occur by the code of the application itself. |
| It isn’t possible to recover from an error. | One can handle the exception by using try-catch blocks & recover the application from them. |
| The compiler does not know the error; hence, it gets classified as “unchecked.” | An exception can be checked or unchecked, which means it may or may not get caught by the compiler. |
| Some examples of errors are “OutOfMemory” and “StackOverflow.” | “ClassNotFound” is the example of a checked exception, while “IndexOutOfBounds” is an unchecked exception. |
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[/fusion_toggle][fusion_toggle title=”Question 29 : Is there a static class in Java?” open=”no” class=”” id=””]
Answer:
Static class is a way of grouping together the classes in Java. As Java doesn’t allow you to create top-level static classes, except the inner or nested classes, a static class is known as a static nested class or static inner class.
[/fusion_toggle][fusion_toggle title=”Question 30 : What is a JavaBean?” open=”no” class=”” id=””]
Answer:
A JavaBean is a class that satisfies the following programming conventions:
It must implement either Externalizable or Serializable.
JavaBean needs to have a no-arg constructor.
All the properties of JavaBean must have public setter & getter methods.
JavaBean instance variables must be private.
[/fusion_toggle][fusion_toggle title=”Question 31 : What is the structure of Java Heap?” open=”no” class=”” id=””]
Answer:
The Java Virtual Machine has a heap, a runtime data area that allocates the memory for all the class instances & arrays. It is created during JVM start-up & shared by all the threads inside the Java Virtual Machines. When the heap storage is not used, it is reclaimed by the garbage collector. JVM throws OutOfMemoryError if the computation needs more heap than what could be supplied by the automatic storage management system.
[/fusion_toggle][fusion_toggle title=”Question 32 : Difference between the throw & throws keyword?” open=”no” class=”” id=””]
Answer:
The following are the key differences between the throw & throws:
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| Sr. No. | Key | Throw | Throws |
|---|---|---|---|
| 1 | Definition | The throw is a keyword used to explicitly throw an exception in the program or inside a block of code. | Throws keyword is used to declare an exception that might get thrown by the function during code execution. |
| 2 | Internal implementation | Internally, the throw keyword can only throw a single exception at a time. | One can declare multiple exceptions with the throws keyword. |
| 3 | Type of exception | With the throw keyword, one can propagate unchecked exceptions only; thus, the checked exception cannot be propagated with the throw keyword. | With the throws keyword, one can declare both checked & unchecked exceptions. |
| 4 | Syntax | The instance variable follows the throw keyword. | The exception class names follow the throws keyword. |
| 5 | Declaration | The throw keyword is used within the method. | Throws keyword is used with the method signature. |
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[/fusion_toggle][fusion_toggle title=”Question 33 : What is the meaning of session management in servlet?” open=”no” class=”” id=””]
Answer:
A session is a dynamic state of the random conversation between the server & the client. The communication channel consists of a string of responses & requests from both sides. There are several ways of session management such as cookie session management API, user authentication, HTML hidden field & URL rewriting., The most popular way of session management implementation is the employment of a session ID into the client’s communicative discourse & the server.
[/fusion_toggle][fusion_toggle title=”Question 34 : What is the core purpose of the JDBC ResultSet Interface?” open=”no” class=”” id=””]
Answer:
The core or central purpose of the JDBC ResultSet Interface is to represent a row in a table or show the result set of a database. Besides, it is also helpful for altering the cursor pointer and churn information from the database.
[/fusion_toggle][fusion_toggle title=”Question 35 : What is the tradeoff between using an unordered array & an ordered array?” open=”no” class=”” id=””]
Answer:
The main advantage of using an ordered array is that the search times are faster with O (log n) than an unordered array O (n). However, an ordered array’s disadvantage is that the insertion operation takes longer O(n) because the elements with higher values are compelled to be moved to make room for new elements. On the other hand, the insertion operation for an unordered array takes a constant time of O(1).
[/fusion_toggle][fusion_toggle title=”Question 36 : Why Java have transient fields?” open=”no” class=”” id=””]
Answer:
Java transient keyword helps to indicate that a field is not a part of the serialization process. The modifier transient applies to a particular member variable of a class to turn off serialization on that member variable. Each field marked as transient will not be serialized.
[/fusion_toggle][fusion_toggle title=”Question 37 : What is multiple inheritance in Java?” open=”no” class=”” id=””]
Answer:
As the name suggests, multiple inheritance is the process wherein a child class inherits multiple parent classes’ properties. If multiple inheritance is supported, it creates a Diamond problem that further creates problems during casting, chaining, etc. So, Java supports multi-inheritance through single inheritance with interfaces to overcome such issues.
[/fusion_toggle][fusion_toggle title=”Question 38 : What is the meaning of Java Servlet?” open=”no” class=”” id=””]
Answer:
Java Servlet is a server-side module that answers client requests. It helps in enhancing the functionality of a web server with minimal maintenance, support, & overhead. It acts as an intermediary between the client & the server. As servlet modules run on the server, it can receive & respond to the client’s requests. Response & request objects of the Java servlet provide a convenient way to handle HTTP requests & send back text data to the client.
[/fusion_toggle][fusion_toggle title=”Question 39 : Why do threads block on I/O in Java?” open=”no” class=”” id=””]
Answer:
Threads block on I/O (that enters the waiting state) so that the other threads may execute when the I/O Operation is performed.
[/fusion_toggle][fusion_toggle title=”Question 40 : Is null a keyword?” open=”no” class=”” id=””]
Answer:
No, a null value is not a keyword. It is a reserved word for the literal values.
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