Interview Questions and Answers for 'Java' | Search Interview Question

Interview Questions and Answers - Order By Newest

Q1311. Which are the thread safe / synchronized / concurrent classes in java collections ?

Core Java

Ans. Stack
Properties
Vector
BlockingQueue
ConcurrentMap
ConcurrentNavigableMap

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Q1312. What are the differences between Intermediate and Terminal Operations in Java 8 streams?

Core Java

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Q1313. What is the difference between Collections.emptyList() and creating instance of a list ?

Core Java

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Q1314. Which are the classes that implement java.util.List interface ?

Core Java

Ans. ArrayList
LinkedList
Vector
Stack

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Q1315. Why do you think that Stack collection class implement List interface ?

Core Java

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Q1316. What is the there only one method declared in Runnable interface?

Core Java

Ans. The Runnable interface describes a class whose instances can be run as a thread. The interface itself is very simple, describing only one method ( run ) that is called automatically by Java when the thread is started. The Runnable interface is usually used in conjunction with the Thread class.

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Q1317. What is difference between Executor.submit() and Executer.execute() method ?

Core Java

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Q1318. What is difference between CyclicBarrier and CountDownLatch in Java ?

Core Java

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Q1319. What do you mean by synchronized Non Access Modifier?

Core Java

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Q1320. Name few classes of java.util.regex package ?

Core Java

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Q1321. Is String thread-safe?

Core Java

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Q1322. Explain toString method ? Which class contains this method ?

Core Java

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Q1323. Explain pre compilation.

Core Java

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Q1324. What will the following code print and Why

class Class1 {
static{
System.out.println("Wow");
}
public static final int xyz=1;
}

class Class2{
public static void main(String[] args) {
System.out.println(String.valueOf(Class1.xyz));
}
}

Core Java

Ans. 1

Reason being that Class1.xyz is replaced with 1 during pre compilation only and a reference to Class1 is never made.

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Q1325. Why java allows explicit import of class final static elements but not others ?

Core Java

Ans. Because they can be replaced easily in pre compilation whereas others cannot.

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Q1326. Why do we have multiple core java jars in java 9 ?

Core Java

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Q1327. What is the concept of modules in Java 9 ?

Core Java

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Q1328. How modules are different than packages in Java 9 ?

Core Java

Ans. Modules are independently build units and contains multiple packages.

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Q1329. How Java 9 helps in building light weight applications ?

Core Java

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Q1330. Do we need different class loaders for different modules in Java 9 ?

Core Java

Ans. No, We can use the same class loader.

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Q1331. What is ModuleDescriptor ?

Core Java

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Q1332. What is ModuleLayer ?

Core Java

Ans. A Module layer is created from a graph of modules and is a function that maps modules to their class loaders.

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Q1333. Difference between named and unnamed modules ?

Core Java

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Q1334. What is the use of Requires, Exports, Opens and provides within Module Descriptor ?

Core Java

Ans. Requires specifies the dependencies for the module, i.e the modules required for this module to function.

Exports specifies the packages exported by the module.

Opens specifies the packages opened by the module.

Provides specifies the services provided by the module

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Q1335. Does Java 9 allows same package within different modules ?

Core Java

Ans. Yes it allows if the modules are mapped to different class loaders.

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Q1336. What are the qualified and unqualified packages ?

Core Java

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Q1337. How does modularity in Java 9 facilitates better encapsulation ?

Core Java

Ans. By providing dependencies , services and exports explicitly

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Q1338. How does Java 9 provides backward compatibility with libraries that haven't published themselves as modules ?

Core Java

Ans. Though Automatic modules. Any JAR on the module path without module descriptor ends up as automatic module

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Q1339. What is the default setting for Automatic modules regarding exporting packages and reading modules ?

Core Java

Ans. As one purpose of automatic module is to provide backward compatibility with the module less dependencies, automatic modules exports all packages and include all other modules.

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Q1340. What is JShell?

Core Java

Ans. JShell is a feature in java 9 using which we can code and test without compiling using javac and see the result of calculations directly.

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