This answer is more focused on the theory aspect of your question.

Fundamentally you are making an assertion: "This methods runs only under certain threads". This assertion isn't really different than any other assertion you might make ("The method accepts only integers less than 17 for parameter X"). Issues are

  • Where do such assertions come from?
  • Can static analyzers check them?
  • Where do you get such a static analyzer?

Mostly such assertions have to come from the software designers, as they are the only people that know the intentions. The traditional term for this is "Design by Contract", although most DBC schemes are only over the current program state (C's assert macro) and they should really be over the programs' past and future states ("temporal assertions"), e.,g., "This routine will allocate a block of storage, and eventually some piece of code will deallocate it". One can build tools that try to determine hueristically what the assertions are (e.g., Engler's assertion induction work; others have done work in this area). That's useful, but the false positives are an issue. As practical matter, asking the designers to code such assertions doesn't seem particularly onerous, and is really good long term documentation. Whether you code such assertions with a specific "Contract" language construct, or with an if statement ("if Debug && Not(assertion) Then Fail();") or hide them in an annotation is really just a matter of convenience. Its nice when the language allows to code such assertions directly.

Checking of such assertions statically is difficult. If you stick with current-state only, the static analyzer pretty much has to do full data flow analysis of your entire application, because the information needed to satisfy the assertion likely comes from data created by another part of the application. (In your case, the "inside EDT" signal has to come from analyzing the whole call graph of the application to see if there is any call-path that leads to the method from a thread which is NOT the EDT thread). If you use temporal properties, the static check pretty much needs some kind of state-space verification logic in addition; these are presently still pretty much research tools. Even with all this machinery, static analyzers generally have to be "conservative" in their anlayses; if they can't demonstrate that something is false, they pretty much have to assume it is true, because of the halting problem.

Where do you get such analyzers? Given all the machinery needed, they're hard to build and so you should expect them to be rare. If somebody has built one, great. If not... as a general rule, you don't want do this yourself from scratch. The best long-term hope is to have generic program analysis machinery available on which to build such analyzers, to amortize the cost of building all the infrastructure. (I build program analyzer tool foundations; see our DMS Software Reengineering Toolkit).

One way to make it "easier" to build such static analyzers is to restrict the cases they handle to narrow scope, e.g., CheckThread. I'd expect CheckThread to do exactly what it presently does, and it would be unlikely to get a lot stronger.

The reason that "assert" macros and other such dynamic "current state" checks are popular is that they can actually be implemented by a simple runtime test. That's pretty practical. The problem here is that you may never exercise a path that leads to a failed conditions. So, for dynamic analysis, absence of detected failure is not really evidence of correctness. Still feels good.

Bottom line: static analyzers and dynamic analyzers each have their strength.

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GitHub
github.com › anishLearnsToCode › hackerrank-java-basic-skill-test › blob › master › src › TestThread.java
hackerrank-java-basic-skill-test/src/TestThread.java at master · anishLearnsToCode/hackerrank-java-basic-skill-test
t = new Thread(this, threadName); t.start(); } } } · public class TestThread { public static void main(String[] args) { SampleDemo A = new SampleDemo("A"); SampleDemo B = new SampleDemo("B"); B.start(); A.start(); } }
Author   anishLearnsToCode
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hackerrank-java-basic-skill-test/test-thread.md at master · anishLearnsToCode/hackerrank-java-basic-skill-test
Contains solved programs for the HackerRank Java (Basics) Skill Test Certification 🎓. - hackerrank-java-basic-skill-test/test-thread.md at master · anishLearnsToCode/hackerrank-java-basic-skill-test
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java threads static analysis hackerrank solution - YouTube
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Top answer
1 of 3
8

This answer is more focused on the theory aspect of your question.

Fundamentally you are making an assertion: "This methods runs only under certain threads". This assertion isn't really different than any other assertion you might make ("The method accepts only integers less than 17 for parameter X"). Issues are

  • Where do such assertions come from?
  • Can static analyzers check them?
  • Where do you get such a static analyzer?

Mostly such assertions have to come from the software designers, as they are the only people that know the intentions. The traditional term for this is "Design by Contract", although most DBC schemes are only over the current program state (C's assert macro) and they should really be over the programs' past and future states ("temporal assertions"), e.,g., "This routine will allocate a block of storage, and eventually some piece of code will deallocate it". One can build tools that try to determine hueristically what the assertions are (e.g., Engler's assertion induction work; others have done work in this area). That's useful, but the false positives are an issue. As practical matter, asking the designers to code such assertions doesn't seem particularly onerous, and is really good long term documentation. Whether you code such assertions with a specific "Contract" language construct, or with an if statement ("if Debug && Not(assertion) Then Fail();") or hide them in an annotation is really just a matter of convenience. Its nice when the language allows to code such assertions directly.

Checking of such assertions statically is difficult. If you stick with current-state only, the static analyzer pretty much has to do full data flow analysis of your entire application, because the information needed to satisfy the assertion likely comes from data created by another part of the application. (In your case, the "inside EDT" signal has to come from analyzing the whole call graph of the application to see if there is any call-path that leads to the method from a thread which is NOT the EDT thread). If you use temporal properties, the static check pretty much needs some kind of state-space verification logic in addition; these are presently still pretty much research tools. Even with all this machinery, static analyzers generally have to be "conservative" in their anlayses; if they can't demonstrate that something is false, they pretty much have to assume it is true, because of the halting problem.

Where do you get such analyzers? Given all the machinery needed, they're hard to build and so you should expect them to be rare. If somebody has built one, great. If not... as a general rule, you don't want do this yourself from scratch. The best long-term hope is to have generic program analysis machinery available on which to build such analyzers, to amortize the cost of building all the infrastructure. (I build program analyzer tool foundations; see our DMS Software Reengineering Toolkit).

One way to make it "easier" to build such static analyzers is to restrict the cases they handle to narrow scope, e.g., CheckThread. I'd expect CheckThread to do exactly what it presently does, and it would be unlikely to get a lot stronger.

The reason that "assert" macros and other such dynamic "current state" checks are popular is that they can actually be implemented by a simple runtime test. That's pretty practical. The problem here is that you may never exercise a path that leads to a failed conditions. So, for dynamic analysis, absence of detected failure is not really evidence of correctness. Still feels good.

Bottom line: static analyzers and dynamic analyzers each have their strength.

2 of 3
3

We haven't tried any static analysis tools, but we've used AspectJ to write a simple aspect that detects at runtime when any code in java.awt or javax.swing is invoked outside the EDT. It has found several places in our code that were missing a SwingUtilities.invokeLater(). We run with this aspect enabled throughout our QA cycle, then turn it off shortly before release.

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GitHub
github.com › jgomez-m › HackerRank › blob › master › src › hacker › rank › java › threads › transactions › Solution.java
HackerRank/src/hacker/rank/java/threads/transactions/Solution.java at master · jgomez-m/HackerRank
public class Solution { private static final Scanner SCANNER = new Scanner(System.in); private static final Account ACCOUNT = new Account(); private static final Transaction TRANSACTION = new Transaction(ACCOUNT); · public static void main(String[] args) throws InterruptedException { int threadsCount = Integer.parseInt(SCANNER.nextLine()); Thread[] threads = new Thread[threadsCount]; ·
Author   jgomez-m
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HackerRank
hackerrank.com › skills-directory › java_intermediate
Java (Intermediate) | Skills Directory | HackerRank
These parts are known as threads and are lightweight processes available within the process. Working with Networking in Java - Java Networking is a notion of connecting two or more computing devices together to share the resources.
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YouTube
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HackerRank Java (Basic) Certification Test | Solution #2 - YouTube
Hey guys in this video we shared the Java (Basic) HackerRank Certification Test again with different set of questions.You can find the another video here - h...
Published   August 22, 2020
Views   25K
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StudyX
studyx.ai › homework › 104148902-nackerrankcom-test-i2g42-90il-qquestions-107905583-hackerrank-hackerrank-java-basic
nackerrankcom/test/i2g42/90il/qquestions/107905583 Java (Basic) Skills Certification Test 5 Java Threads - Static Analysis ALL What is the output of the following Java snippet class SampleDemo
September 1, 2024 - 6 Java Threads - Static Analysis ALL What is the output of the following Java snippet 1 class SampleDemo implements Runnable private Thread t private String threadName SampleDemo (String threadName)
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HackerRank
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Solve Advanced Questions | Java
Join over 28 million developers in solving code challenges on HackerRank, one of the best ways to prepare for programming interviews.
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StudyX
studyx.ai › homework › 102093455-6-java-threads-static-analysis-what-is-the-output-of-the-following-java-snippet-class
6 Java Threads - Static Analysis What is the
January 24, 2025 - 6 Java Threads - Static Analysis ALL What is the output of the following Java snippet 1 class SampleDemo implements Runnable private Thread t private String threadName SampleDemo (String threadName)
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Medium
medium.com › @vidhyamanickaraj › java-string-concepts-with-example-f05f77c8c5f3
Java String Concepts With Example HackerRank String Questions With Solutions | by vidhya manickaraj | Medium
April 17, 2024 - By default, Stringbuffer is Synchronized, which means at one time,only one thread will get executed.(Thread means some piece of logic/code/functionality).
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YouTube
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HackerRank Java (Basic) Skills Certification Test | Solutions - YouTube
Thanks if you are watching us. There is an error in solution 1 which is why one testcase fails. Use a counter to get if all the numbers are same or not. .......
Published   July 24, 2020
Views   1K
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YouTube
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Java (Basic) Certification | Hackerrank Certifications - YouTube
Thanks if u r watching us ... #Dev19 #C #Python #Dev19 #HackerankSolutions #C #C++ #Java #PythonPlease Subscribe Us ....
Published   June 16, 2020
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Scribd
es.scribd.com › document › 702344224 › JAVA-HACKERRANK-SOLUTIONS
Java Hackerrank Solutions | PDF | Software | Software Engineering
JAVA HACKERRANK SOLUTIONS - Free download as Text File (.txt), PDF File (.pdf) or read online for free. The document contains 16 code snippets from Java lessons on various topics: 1. The first snippet prints a welcome message in Java. 2. The second snippet takes user input and prints it back out.
Rating: 2.3 ​ - ​ 3 votes
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PREP INSTA
prepinsta.com › home › hackerrank test papers and placement papers › top 25 hackerrank coding questions and answers
Top 25 Hackerrank Coding Questions with Solutions | PrepInsta
March 27, 2025 - import java.util.*; class Solution { public static int cost(int grid[][], int row1, int col1,int row2, int col2) { if (row1 == row2 && col1 == col2) { if (grid[row1][col1] == 1) return 1; return 0; } int ans = 0; if (grid[row1][col1] == 1) ans++; if (grid[row2][col2] == 1) ans++; return ans; } public static int solve(int n, int m, int grid[][],int dp[][][], int row1,int col1, int row2) { int col2 = (row1 + col1) - (row2); if (row1 == n - 1 && col1 == m - 1 &&row2 == n - 1 && col2 == m - 1) return 0; if (row1 >= n || col1 >= m ||row2 >= n || col2 >= m) return -1 * Integer.MAX_VALUE; if (dp[row1
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StudyX
studyx.ai › homework › 104594001-hackerrank-hackerrank-java-basic-skills-certification-test-answered-4-6-27-mins-class
HackerRank HackerRank Java Basic Skills
September 7, 2024 - 6 Java Threads - Static Analysis ALL What is the output of the following Java snippet 1 class SampleDemo implements Runnable private Thread t private String threadName SampleDemo (String threadName)
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HackerRank
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Solve Java Code Challenges
Join over 28 million developers in solving code challenges on HackerRank, one of the best ways to prepare for programming interviews.
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TECH UPDATE
tejatechview.com › 2022 › 01 › mini-project-java-complete-beginner.html
Mini project- Java Complete Beginner Hands-On Solutions - TECH UPDATE
Can you suggest a way to load Hackerrank Web IDE's framework libraries like Junit into Java class project?ReplyDelete ... Solution for Regulaar expression complete runable code package com.fresco; import java.util.ArrayList; import java.util.regex.Pattern; public class RegEx { public static boolean isVisa(String s) { if (s.startsWith("4")) { if (s.length() == 13 || s.length() == 16) { return true; } else { return false; } } else { return false; } } public static boolean isAmericanExpress(String s) { if (s.startsWith("34") || s.startsWith("37")) { if (s.length() == 15) { return true; } else { r
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