Java

Why does the following Java 8 pipeline report a type mismatch in Eclipse?

The following code uses Java 8 streams and lambdas to find an unlimited number of “sum primes” : import java.util.stream.Stream; public class FunctionalPrime { public static void main(String[] args) { printSumPrimes(6); } /** * Given n>0, print all pairs i & j s.t. 1<=i<=j<=n and i+j is prime * * NOTE: This BREAKS in Eclipse because of some Eclipse bug!…
Read more

Refactoring a Java project causes hundreds of "X not public" errors

I’m busy upgrading an ancient java app, and after getting it compiling I set about reorganizing the code structure. There are currently 500 files in ONE massive folder, so I need to split it into a neater folder structure. The moment I moved some files, the compiler generates heaps of “X() is not public in <BaseClass>” errors. Yes, the refactoring…
Read more

why string length -1

I have found the following program to check if a string is palindrome. import java.util.Scanner; public class PalindromeString{ public static void main(String[] args){ Scanner in = new Scanner(System.in); System.out.println(“Enter the string which you want to check whether that is palindrome or not: “); String s = in.next(); String r = “”; for(int i=s.length()-1; i>=0; i–){ r = r+s.charAt(i); } System.out.println(“Reverse…
Read more

Android SQLiteOpenHelper is not working

The onCreate void of my SQLiteOpenHelper is not called even when get a databse with “database = helper.getWritableDatabase();”. I read lots of posts on this page here but I didn’t find any soloution that worked for me. SQLiteOpenHelper: package eu.michael1011.currencies.sql; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.util.Log; public class Helper extends SQLiteOpenHelper { public static final String database_name =…
Read more

Creating a boolean array by prime number

Write a code fragment that creates an N-by-N Boolean array a[][] such that a[i][j] is true if i and j are relatively prime and false otherwise. My code is public static void main(String[] args){ int N = 12; boolean[][] a = new boolean[N][N]; for(int i = 0; i < a.length; i++){ for(int j = 0; j < a[i].length; j++){ if(i%j…
Read more

Aspect around call on annotated field

I want AspectJ to inject the measuring code around all invocations of any method, on fields annotated with @Measured and capture the method’s name. This is what I have: @Pointcut(“get(@my.annotation.Measured * *) && @annotation(measured)”) public void fieldAnnotatedWithMeasured(Measured measured) {} @Around(value = “fieldAnnotatedWithMeasured(measured)”, argNames = “joinPoint,measured”) public Object measureField(ProceedingJoinPoint joinPoint, Measured measured) throws Throwable {…} Use case: public class A {…
Read more

Maven failing to find jar from Project Repository

I have a jar file which I need to include in my project. I am using eclipse with Maven I created the following folder in my project on my computer: /home/robert/eclipse/BobProjects/BobDiary/in_project_maven_repository/metcarob.com.lib/nachocalendar/0.23 and I placed a file there called: nachocalendar-0.23.jar I then added the dependancy to my POM file: <dependency> <groupId>metcarob.com.lib</groupId> <artifactId>nachocalendar</artifactId> <version>0.23</version> <scope>compile</scope> </dependency> I also added the Repo into…
Read more

Spring 4.3.0.RELEASE + Hibernate 5.2.0.Final – Inert duplicate rows each time

Hi, There is a lot of version of this problem but all the wats to fix it are failed. Every time I insert object, it insert me duplicate data I tried to change the add function with “persist(role)” or “saveOrUpdate(role)” but it is`nt working. What could be the problem? StartupDbDataInit package com.searcher.startup; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.ApplicationListener;…
Read more

Java generic type casting [duplicate]

This question already has an answer here: Why does this generic code compile in java 8? 3 answers why java compiler (1.8) doesn’t find an error when i use newList1()? public class Test { public static void main(String[] args) { String str1 = newList1(); //1. it’s ok String str2 = newList2(); //2. compiler will warn } private static <T extends…
Read more

Regular Expression for AlphaNumeric, Hyphen and Underscore without any space

I would like to have a regular expression that checks if the string contains Alphanumerics, Hyphen and Underscore. There should not be any spaces or other special characters other these three. My string will be under either of these 2 patterns. ‘XYZ0123_123456’ ‘ABCdefGHI-727’ I have already tried this expression. But it didnt workout. [[a-zA-Z0-9_-]*] Source: java