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Friday, 15 November 2013

Data Structure and Algorithms : Queue Program in Java

Program:

public class queuepgm {
private int maxSize;
private long[] queArray;
private int front;
private int rear;
private int nItems;

public queuepgm(int s)

{
maxSize = s;
queArray = new long[maxSize];
front = 0;
rear = -1;
nItems = 0;
}

public void enqueue(long j)

{
if(rear == maxSize-1)
rear = -1;
queArray[++rear] = j;
nItems++;
}

public long dequeue()
{
long temp = queArray[front++];
if(front == maxSize)
front = 0;
nItems--;
return temp;
}
public long peekFront()

{
    return queArray[front];
}
public boolean isEmpty()      
{
return (nItems==0);
}
public boolean isFull()
{
return (nItems==maxSize);
}
public int size()
{
return nItems;
}
public static void main(String[] args)
{
queuepgm theQueue = new queuepgm(5); // queue holds 5 items
theQueue.enqueue(10);
theQueue.enqueue(20);
theQueue.enqueue(30);
theQueue.enqueue(40);
System.out.println("Dequeue Values: FIFO");
while( !theQueue.isEmpty() )
{
long n = theQueue.dequeue();
System.out.print(n+"\n");

}
}

}

Output:


Data Structure and Algorithms : Stack Program in Java

Program

public class stackpgm {
private int maxSize;
private long[] stackArray;
private int top;
public stackpgm(int s)

{
maxSize = s;

stackArray = new long[maxSize];
top = -1;

}

public void push(long j)

{
    if(!isFull())
    {
      stackArray[++top] = j;
    }

}
public long pop()
{
   
      return stackArray[top--];  
   
     
}

public long peek()

{
return stackArray[top];
}

public boolean isEmpty()

{
return (top == -1);
}

public boolean isFull()
{
return (top == maxSize-1);
}

public static void main(String[] args)
{
stackpgm theStack = new stackpgm(10);
theStack.push(1);
theStack.push(2);
theStack.push(3);
theStack.push(4);
System.out.println("Pop up values");
while( !theStack.isEmpty() )
{
long value = theStack.pop();
System.out.print(value+"\n");
}
}


}

Output


Head and Tail Commands in Linux


Head Command

Description : prints output of first part of the file by default it will print first 10 lines

Syntax : head filename

examples:

1.  head upcasting.java


it will print first 10 lines of the file upcasting.java by default.

2. head -n 50 upcasting.java
 it will print first 50 lines of the file upcasting.java.

3. head upcasting.java downcasting.java
it will print first 10 line of the 2 files upcasting.java and downcasting.java.

4. head *.java
it will print all the java files first 10 lines.

5. head *.java *.class
it will print all the java and class files first 10 lines.


Tail Command:

Description : prints output of last part of the file by default it will print last 10 lines

Syntax : tail filename

Examples:

1. tail upcasting.java
it will print last 10 lines of the file upcasting.java by default.

2. tail -n 50 upcasting.java
 it will print last 50 lines of the file upcasting.java.

3. tail upcasting.java downcasting.java
it will print last 10 line of the 2 files upcasting.java and downcasting.java.

4. tail *.java
it will print all the java files last 10 lines.

5. tail *.java *.class
it will print all the java and class files last 10 lines.

Practice Examples:

1. How to Print the 11th line of the file ?

    head -n 11 upcasting.java | tail -n 1

2. How to print lines from 5 to 11th of the file ?

    head -n 11 upcasting.java | tail -n 5

3.  How to print number of lines head and tail command file (by default it will  print 10 lines)?
   
    head upcasting.java | wc -l
    tail upcasting.java | wc -l


    both will return 10

    head -n 20 upcasting.java | wc -l
    tail -n 20 upcasting.java | wc -l


   both will return 20

   for number of word wc -w and number of characters wc -c

   head upcasting.java | wc -c
   it will print number of first 10 lines characters in digits

   tail upcasting.java | wc -c
   it will print number of last 10 lines characters in digits
 

   head upcasting.java | wc -w
   it will print number of first 10 lines words in digits

   tail upcasting.java | wc -w
   it will print number of last 10 lines words in digits

4. How to get First and last 5 files of java in a java directory?

   ls *.java | tail -n 5  
   ls *.java | head -n 5
 
   ls -l *.java | tail -n 5  
   ls -l *.java | head -n 5

5. ls -la *.class | tail -n 12 | wc -l  it will return 12

6.  ls -la *.class | tail -n 12
it will shows last 12 class files list

7.  ls -la *.class | head -n 12 
it will shows first 12 class files list.  

8.      head -c 10 downcasting.java
9.      tail -c 10 downcasting.java
10.   head -c 400  downcasting.java | tail -n 3

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