Not able to read a file present in the directory in Jenkins

I am trying to read a file in a jenkins pipeline. I create this file using Linux 'tee' command.
I try to read the file using in built java functions such as Files.readAllLines in java.nio or BufferedReader in java.io package.
None of the either 2 cases work.

The reason I want to use either of these 2 or a similar technique is because I have to read this file in a shared library and not in Jenkins file.
I try to read the file in a Jenkins pipeline so as to test whether these 2 methods work or not.

How can I use these techniques to read already existing file in my workspace ?

Also, I tried to use jenkins readFile method and it works but I think I cannot use it in my shared library.

My Jenkins file is:

import java.io.file.*

pipeline {
agent any

stages {
    stage('Scan Timeout Test') {
        steps {
            script {
				sh '''echo "Running ls before ..."
ls -lt
				'''
                sh 'ls -lt | tee lslog.txt'
				sh '''pwd
				ls -lt
				'''
				getLogs("$WORKSPACE/lslog.txt")
            }
        }
    } //end of stage
  }
}

def getLogs(logPath) throws IOException {
    //println "Reading $logPath..."
    //def text = readFile logPath
    //println text
     /*println "[INFO] Reading Log File: " + Paths.get(logPath).toAbsolutePath().toString()
     try {
       return Files.readAllLines(Paths.get(logPath), StandardCharsets.UTF_8);
     } catch(IOException e){
         println "[ERROR] Failed to read file '"+logPath+"': "+e.getMessage()
         throw e
     }*/
     BufferedReader bufReader = new BufferedReader(new FileReader(logPath)); 
     ArrayList<String> listOfLines = new ArrayList<>(); 
 
     String line = bufReader.readLine(); 
 
     while (line != null) { 
	     listOfLines.add(line); 
	     line = bufReader.readLine(); 
     }
 
     bufReader.close();
     return listOfLines
}


The output that I get in my Jenkins console is: 
+ pwd
/jenkins/workspace/test
+ ls -lt
total 44
-rw-r--r-- 1 root root   526 Aug 21 11:32 lslog.txt
drwxr-xr-x 2 root root   173 Aug 21 11:32 vars
drwxr-xr-x 3 root root   109 Aug 21 11:32 resources
drwxr-xr-x 4 root root    29 Aug 21 11:32 src
-rw-r--r-- 1 root root 22783 Aug 21 11:32 README.md
-rw-r--r-- 1 root root   602 Aug 21 11:32 build.gradle
drwxr-xr-x 3 root root    21 Aug 21 11:32 gradle
-rw-r--r-- 1 root root  5296 Aug 21 11:32 gradlew
-rw-r--r-- 1 root root  2176 Aug 21 11:32 gradlew.bat
drwxr-xr-x 2 root root   118 Aug 21 11:32 integration-tests
[Pipeline] }
[Pipeline] // script
[Pipeline] }
[Pipeline] // stage
[Pipeline] }
[Pipeline] // withEnv
[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
java.io.FileNotFoundException: /jenkins/workspace/test/lslog.txt (No such file or directory)
at java.io.FileInputStream.open0(Native Method)

Using ls -lt, I can see that my file, lslog.txt is created in the directory but I cannot read it.

You can use readFile in shared libraries as long as you pass the steps along.
Check the documentation at https://www.jenkins.io/doc/book/pipeline/shared-libraries/#accessing-steps

package org.foo
class bar {
  static void readFile(filePath, steps) {
    def text = steps.readFile(file: filePath)
  }
}