Update MySQL database engine

 SELECT ENGINE FROM information_schema.TABLES WHERE TABLE_NAME = 'tabel_name' AND TABLE_SCHEMA='db_name';

ALTER TABLE table_name ENGINE = INNODB;

install java in ubuntu

 #Login as root

sudo su

#create jdk directory
mkdir /opt/jdk

#uncompress, change to your file name
tar -zxf jdk-8u5-linux-x64.tar.gz -C /opt/jdk

#check if files are there
#ls /opt/jdk

#update alternatives so the command java point to the new jdk 
update-alternatives --install /usr/bin/java java /opt/jdk/jdk1.8.0_05/bin/java 100


#update alternatives so the command javac point to the new jdk 
update-alternatives --install /usr/bin/javac javac /opt/jdk/jdk1.8.0_05/bin/javac 100

#check if java command is pointing to " link currently points to /opt/jdk/jdk1.8.0_05/bin/java"
update-alternatives --display java

#check if java command is pointing to " link currently points to /opt/jdk/jdk1.8.0_05/bin/javac"
update-alternatives --display javac

#check if java is running
java -version

sudo  update-alternatives --config java

Docker sample

 FROM maven:3.6.0-jdk-8-alpine AS MAVEN_BUILD

MAINTAINER Sushil
COPY pom.xml /build/
COPY src /build/src/
WORKDIR /build/
RUN mvn package
FROM openjdk:8-jre-alpine
WORKDIR /app
COPY --from=MAVEN_BUILD /build/target/name.jar /app/
EXPOSE 8080
ENTRYPOINT ["java", "-jar", "name.jar"]

docker command

 

sudo docker image build -t sushil/verification ./

sudo docker container run -d -p 8087:8080 sushil/verification

list of images::

sudo docker ps

sudo docker logs -f d44b2b216e16

sudo docker exec -it d44b2b216e16 sh

tail -f verification.log

help:  https://dzone.com/articles/build-package-and-run-spring-boot-apps-with-docker

stop::

docker stop <container-name>

Cassandra

 https://www.simplilearn.com/tutorials/big-data-tutorial/cassandra-architecture

Heap Sort(max heap)

 public class HeapSortNew {

    public static void main(String[] args) {

        int[] arr = {4,1,7,2,3,8,10};

        int n= arr.length;

        for(int i=n/2-1;i>=0;i--){

            heapify(arr,n,i);

        }

        System.out.println(Arrays.toString(arr));

        for(int i=n-1;i>=0;i--){

            swap(arr,i,0);

            heapify(arr,i,0);

        }

        System.out.println(Arrays.toString(arr));

    }

    static void heapify(int[] arr, int n, int i){

        int l = 2*i+1;

        int r = 2*i+2;

        int largest = i;

        if(l<n){

            if(arr[l]>arr[largest]){

                largest = l;

            }

        }

        if(r<n){

            if(arr[r]>arr[largest]){

                largest = r;

            }

        }

        //if value get updated

        if(largest!=i){

            swap(arr,i,largest);

            heapify(arr,n,largest);

        }

    }

    static void swap(int[] arr, int i, int j){

        int temp = arr[i];

        arr[i]  =arr[j];

        arr[j]=temp;

    }

}

output:

[10, 3, 8, 2, 1, 4, 7]

[1, 2, 3, 4, 7, 8, 10]he

Find kth largest element in array in java using MaxHeap

 public class FIndKthLargestEmement {

    public static void main(String[] args) {

        int[] arr = {4,1,7,2,3,8,10};

        int n= arr.length;

        for(int i=n/2-1;i>=0;i--){

            heapify(arr,n,i);

        }

        System.out.println(Arrays.toString(arr));

        int k = 2;

//run the loop k times from last index , move root element to ith and heapify the array to maintain maxheap 

        for(int i=n-1;i>=n-k;i--){

            swap(arr,i,0);

            heapify(arr,i,0); //i due to don't like to incluede already sorted element

        }

        System.out.println(Arrays.toString(arr));

        System.out.println(arr[n-k]);

    }

    static void heapify(int[] arr, int n, int i){

        int l = 2*i+1;

        int r = 2*i+2;

        int largest = i;

        if(l<n){

            if(arr[l]>arr[largest]){

                largest = l;

            }

        }

        if(r<n){

            if(arr[r]>arr[largest]){

                largest = r;

            }

        }

        //if value get updated

        if(largest!=i){

            swap(arr,i,largest);

            heapify(arr,n,largest);

        }

    }

    static void swap(int[] arr, int i, int j){

        int temp = arr[i];

        arr[i]  =arr[j];

        arr[j]=temp;

    }

}

output:

[10, 3, 8, 2, 1, 4, 7]

[7, 3, 4, 2, 1, 8, 10]

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