Java入学考试的五道题

打印前100个prime numbers

public static void main(String[] args) 
{
    Scanner scan = new Scanner(System.in);

    int N = scan.nextInt();
    int x = 2;

    for(int i = 0; i <= N; i++)
    {
        int count = 0;

        for(int j = 1; j <= x; j++)
            if(x%j == 0)
                count++;

        if(count == 2)
            System.out.print(x + " ");

        x++;
    }
}

import java.util.Scanner;

public class ExArraySortElement 
{
    public static void main(String[] args) 
    {
        int n, temp;
        //scanner class object creation
        Scanner s = new Scanner(System.in);

        //input total number of elements to be read
        System.out.print("Enter the elements you want : ");
        n = s.nextInt();

        //integer array object
        int a[] = new int[n];

        //read elements 
        System.out.println("Enter all the elements:");
        for (int i = 0; i < n; i++) 
        {
            a[i] = s.nextInt();
        }

        //sorting elements
        for (int i = 0; i < n; i++) 
        {
            for (int j = i + 1; j < n; j++) 
            {
                if (a[i] > a[j]) 
                {
                    temp = a[i];
                    a[i] = a[j];
                    a[j] = temp;
                }
            }
        }

        //print sorted elements         
        System.out.println("Ascending Order:");
        for (int i = 0; i < n ; i++) 
        {
            System.out.println(a[i]);
        }
    }   
}

https://www.includehelp.com/java-programs/sort-an-array-in-ascending-order.aspx

import java.util.Scanner;
class PrimeCheck
{
   public static void main(String args[])
   {        
    int temp;
    boolean isPrime=true;
    Scanner scan= new Scanner(System.in);
    System.out.println("Enter any number:");
    //capture the input in an integer
    int num=scan.nextInt();
        scan.close();
    for(int i=2;i<=num/2;i++)
    {
           temp=num%i;
       if(temp==0)
       {
          isPrime=false;
          break;
       }
    }
    //If isPrime is true then the number is prime else not
    if(isPrime)
       System.out.println(num + " is a Prime Number");
    else
       System.out.println(num + " is not a Prime Number");
   }
}

https://beginnersbook.com/2014/01/java-program-to-check-prime-number/

public boolean isPalindrome(String text) {
    String clean = text.replaceAll("\\s+", "").toLowerCase();
    int length = clean.length();
    int forward = 0;
    int backward = length - 1;
    while (backward > forward) {
        char forwardChar = clean.charAt(forward++);
        char backwardChar = clean.charAt(backward--);
        if (forwardChar != backwardChar)
            return false;
    }
    return true;
}

import java.util.*;
 
class Palindrome
{
   public static void main(String args[])
   {
      String original, reverse = ""; // Objects of String class
      Scanner in = new Scanner(System.in);
 
      System.out.println("Enter a string to check if it is a palindrome");
      original = in.nextLine();
 
      int length = original.length();
 
      for ( int i = length - 1; i >= 0; i-- )
         reverse = reverse + original.charAt(i);
 
      if (original.equals(reverse))
         System.out.println("Entered string is a palindrome.");
      else
         System.out.println("Entered string isn't a palindrome.");
 
   }
}    

public int countWord(String word, File file) {
int count = 0;
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
    String nextToken = scanner.next();
    if (nextToken.equalsIgnoreCase(word))
    count++;
}
return count;
}