Java Archives - Page 9 of 9

Heapsort

January 20, 2018May 4, 2017 by T Tak

Task: We have to sort an array of some values using Heapsort in Java. The time complexity of Heap Sort algorithm is O(n * log(n)) as in the average case so in worst and best cases. The essence of heap sort is in finding the maximum value in non-sorted part of the array, putting it … Read more

Java Collection Interview Questions and Answer

April 7, 2023April 25, 2017 by T Tak

Here is a list of Java Collections interview Questions. These are some of the famous questions asked in interviews. Java Collections Interview Questions What is the Java Collections Framework? The Java Collections Framework is a set of interfaces and classes that provide a foundation for working with collections of objects. It offers reusable data structures, … Read more

Java 9 Features

January 20, 2018March 23, 2017 by T Tak

Here are all the Java 9 features that will be making to the release in July 2017. Process API Updates HTTP/2 Client (Incubator) Improve Contended Locking Unified JVM Logging Compiler Control Variable Handles Segmented Code Cache Smart Java Compilation, Phase Two The Modular JDK Modular Source Code Elide Deprecation Warnings on Import Statements Resolve Lint … Read more

Setting MAVEN_OPTS in Linux

January 20, 2018March 2, 2017 by T Tak

If you want to set the MAVEN_OPTS in Linux permanently, you can do it like below Add below line to ~/.profile

export MAVEN_OPTS="-Xmx1g -XX:MaxPermSize=400m"

1	export MAVEN_OPTS="-Xmx1g -XX:MaxPermSize=400m"

They you need to logout and login again.

Convert a string representing a duration, ie: 300ms, 20s, etc to to nanoseconds

January 20, 2018February 24, 2017 by T Tak

Suppose you have a string in your application that has the duration of time using ns, us ms , s h, d. And you want to convert them all to nano seconds, then utility will of great help to you.

package com.javagists.learn.utils;

import java.util.concurrent.TimeUnit;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class ConvertDuration2TimeUnit {
 private static final Pattern DURATION_STRING_PATTERN = Pattern.compile("^(\d+)\s?(ns|us|ms|s|m|h|d)?$");

 public static long convertDurationString2Nanos(String duration) {
  final Matcher matcher = DURATION_STRING_PATTERN.matcher(duration);
  if (!matcher.matches()) {
   throw new IllegalArgumentException("duration string format invalid");
  }

  final long sourceDuration = Long.parseLong(matcher.group(1));
  final String sourceUnitString = matcher.group(2);
  final TimeUnit sourceTimeUnit;
  if ("ns".equalsIgnoreCase(sourceUnitString)) {
   sourceTimeUnit = TimeUnit.NANOSECONDS;
  } else if ("us".equalsIgnoreCase(sourceUnitString)) {
   sourceTimeUnit = TimeUnit.MICROSECONDS;
  } else if ("ms".equalsIgnoreCase(sourceUnitString)) {
   sourceTimeUnit = TimeUnit.MILLISECONDS;
  } else if ("s".equalsIgnoreCase(sourceUnitString)) {
   sourceTimeUnit = TimeUnit.SECONDS;
  } else if ("m".equalsIgnoreCase(sourceUnitString)) {
   sourceTimeUnit = TimeUnit.MINUTES;
  } else if ("h".equalsIgnoreCase(sourceUnitString)) {
   sourceTimeUnit = TimeUnit.HOURS;
  } else if ("d".equalsIgnoreCase(sourceUnitString)) {
   sourceTimeUnit = TimeUnit.DAYS;
  } else {
   sourceTimeUnit = TimeUnit.MILLISECONDS;
  }

  return sourceTimeUnit.toNanos(sourceDuration);
 }
}

package com.javagists.learn.utils;

import java.util.concurrent.TimeUnit;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

public class ConvertDuration2TimeUnit {

private static final Pattern DURATION_STRING_PATTERN = Pattern.compile("^(\d+)\s?(ns|us|ms|s|m|h|d)?$");

public static long convertDurationString2Nanos(String duration) {

final Matcher matcher = DURATION_STRING_PATTERN.matcher(duration);

if (!matcher.matches()) {

throw new IllegalArgumentException("duration string format invalid");

}

final long sourceDuration = Long.parseLong(matcher.group(1));

final String sourceUnitString = matcher.group(2);

final TimeUnit sourceTimeUnit;

if ("ns".equalsIgnoreCase(sourceUnitString)) {

sourceTimeUnit = TimeUnit.NANOSECONDS;

} else if ("us".equalsIgnoreCase(sourceUnitString)) {

sourceTimeUnit = TimeUnit.MICROSECONDS;

} else if ("ms".equalsIgnoreCase(sourceUnitString)) {

sourceTimeUnit = TimeUnit.MILLISECONDS;

} else if ("s".equalsIgnoreCase(sourceUnitString)) {

sourceTimeUnit = TimeUnit.SECONDS;

} else if ("m".equalsIgnoreCase(sourceUnitString)) {

sourceTimeUnit = TimeUnit.MINUTES;

} else if ("h".equalsIgnoreCase(sourceUnitString)) {

sourceTimeUnit = TimeUnit.HOURS;

} else if ("d".equalsIgnoreCase(sourceUnitString)) {

sourceTimeUnit = TimeUnit.DAYS;

} else {

sourceTimeUnit = TimeUnit.MILLISECONDS;

}

return sourceTimeUnit.toNanos(sourceDuration);

}

Longest Palindromic Subsequence – Leetcode Java

August 10, 2018February 10, 2017 by T Tak

Given a string s, find the longest palindromic subsequence’s length in s. You may assume that the maximum length of s is 1000. Example 1: Input:

"bbbab"

"bbbab"

Output:

4

One possible longest palindromic subsequence is “bbbb”. Example 2: Input:

"cbbd"

"cbbd"

Output:

2

One possible longest palindromic subsequence is “bb”. Java Solution

package com.javagists.learn.interview.questions;


public class LongestPalindromeSubsequence {
 public int longestPalindromeSubseq(String input) {
  int[][] dp = new int[input.length()][input.length()];
  for (int i = input.length() - 1; i &gt;= 0; i--) {
   dp[i][i] = 1;
   for (int j = i + 1; j &lt; input.length(); j++) {
    if (input.charAt(i) == input.charAt(j)) {
     dp[i][j] = dp[i + 1][j - 1] + 2;
    } else {
     dp[i][j] = Math.max(dp[i + 1][j], dp[i][j - 1]);
    }
   }
  }
  return dp[0][input.length() - 1];
 }

 public static void main(String[] args) {
  LongestPalindromeSubsequence longestPalindromeSubsequence = new LongestPalindromeSubsequence();
  System.out.println(longestPalindromeSubsequence.longestPalindromeSubseq("bbbaabbgghj"));
 }
}

package com.javagists.learn.interview.questions;

public class LongestPalindromeSubsequence {

public int longestPalindromeSubseq(String input) {

int[][] dp = new int[input.length()][input.length()];

for (int i = input.length() - 1; i >= 0; i--) {

dp[i][i] = 1;

for (int j = i + 1; j < input.length(); j++) {

if (input.charAt(i) == input.charAt(j)) {

dp[i][j] = dp[i + 1][j - 1] + 2;

} else {

dp[i][j] = Math.max(dp[i + 1][j], dp[i][j - 1]);

}

return dp[0][input.length() - 1];

}

public static void main(String[] args) {

LongestPalindromeSubsequence longestPalindromeSubsequence = new LongestPalindromeSubsequence();

System.out.println(longestPalindromeSubsequence.longestPalindromeSubseq("bbbaabbgghj"));

}

You can … Read more

License Key Formatting Leetcode – Java

January 20, 2018February 10, 2017 by T Tak

Now you are given a string S, which represents a software license key which we would like to format. The string S is composed of alphanumerical characters and dashes. The dashes split the alphanumerical characters within the string into groups. (i.e. if there are M dashes, the string is split into M+1 groups). The dashes … Read more

Frontend interview questions

January 20, 2018January 31, 2017 by T Tak

Questions you may get asked: 10 Interview Questions Every JavaScript Developer Should Know Front-End Job Interview Questions Front End Web Development Quiz Interview Questions for Front-End-Developer JavaScript Web Quiz Questions you ask: An open source list of developer questions to ask prospective employers Preparing: Preparing for a Front-End Web Development Interview in 2017 Interview Cake — … Read more

Why is String immutable in java?

January 20, 2018January 30, 2017 by T Tak

This question has been asked in a number of interviews in the past and is still being asked. If you search google for this question you will find people trying to answer this question. But no one has been able to answer it properly and no one except the Java designers can really answer. We … Read more