Shortest Function to find if a number is prime

class prime
{
public static boolean PrimeCheck(int a)//a should be greater than 0
{
for(int i=2; i<=a/2; i++)
if(a%i==0)
return false;
return true;
}
}

java program To find all the sets of consecutive natural numbers which add up to give the given number

import java.io.*;
class combi
{
private static int N;
private static int sum;

public static void main(String args[])throws IOException
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
String S;
System.out.print("Enter an integer: ");
S=br.readLine();
int i=Integer.parseInt(S);
combi A= new combi(i, 0);
A.calc();
}

public combi(int a, int b)
{
N=a;
sum=b;
}


public void calc()throws IOException
{
for(int i=1; i<=N/2;i++)
{
for(int j=i; j<=(N+1)/2; j++)
{
sum+=j;
if(sum==N)
{
for(int a=i; a<=j; a++)
{
System.out.print(a);
System.out.print(a }
System.out.println("");
System.out.println("");
sum=0;
break;
}
}
sum=0;
}

}
}

java program To find whether two strings are anagrams

import java.io.*;
class anagrams
{
public void main(String args[])throws IOException
{
String s1,s2;
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("Anagram Tester! Enter the strings:");
System.out.print("String 1: ");
s1=br.readLine();
System.out.print("String 2: ");
s2=br.readLine();
s1=removewhitespace(s1);
s2=removewhitespace(s2);
s1=s1.toLowerCase();
s2=s2.toLowerCase();

if(s1.length()!=s2.length())System.out.print("Not anagrams(no. of letters not same)!");
else
{
for(int i=0;i {
for(int j=0;j {
if(s1.charAt(i)==s2.charAt(j)){s2=delete(s2,j);break;}
}
}
if(s2.equals("")) System.out.print("The strings are anagrams!");
else System.out.print("Not anagrams "+s2);
}
}

public String removewhitespace(String s)
{
for(int i=0;i {
if(s.charAt(i)==' ')s=delete(s,i);
}
return s;
}

public String delete(String s,int ind)
{
String str=s.substring(ind+1,s.length());
s=s.substring(0,ind);
s=s+str;
return s;
}
}

java program on Amicable numbers

class amicable

{

public static void main(String args[])

{

for(int i=2; i<=1000; i++)

{

for(int j=i+1; j<=1000; j++)

{

if(facSum(i)==j&&facSum(j)==i)

{ System.out.println(i+" and "+j+" are Amicable!");

}

}

}

}

public static int facSum(int a)

{

int c=0;

for(int s=1; s<=a/2; s++)

{

if(a%s==0)

c+=s;

}

return c;

}

}