急求几道java编程题，希望大神们帮帮忙！

做一道不嫌少！

第一题：

import java.util.Scanner;
public class sqr {
public static void main(String args[])
{
Scanner scan=new Scanner(System.in);
int num=scan.nextInt();
int result=0;
for(int i=1;i<=num;i++)
result+=i*i;
System.out.println("result is: "+result);
}
}

第二题：

import java.util.Scanner;
class prime
{
public static void main(String args[])
{
Scanner scan=new Scanner(System.in);
int num=scan.nextInt();
for(int i=1;i<=num;i++)
if(isPrime(i)) System.out.print(i+" ");
}
public static boolean isPrime(int val)
{
for(int i=2;i<val;i++)
if(val%i==0) return false;
return true;
}
}

第三题：

import java.util.Scanner;
public class IntegerSort
{
public static void main(String args[])
{
Scanner scan=new Scanner(System.in);
String s=scan.nextLine();
String[] str=s.split(" ");
int[] array=new int[str.length];
for(int i=0;i<str.length;i++)
array[i]=Integer.parseInt(str[i]);
do_quick(array,0,array.length-1);
for(int i=0;i<array.length;i++)
System.out.print(array[i]+" ");
}
static void do_quick(int[] array,int start,int end)
{
if(start==end)
return;
int key =start;
int i=start,j=end;
        while(i<end || j>start)
        {
         while(i!=j)
            {
         if(array[key]>array[j])
                {
         array[key]=array[key]^array[j];
                    array[j]=array[j]^array[key];
                    array[key]=array[key]^array[j];
                    key=j; 
                    break;
                 }
                 j--;
            }
            while(i!=j)
            {
             if(array[key]<array[i])
                {
             array[key]=array[key]^array[i];
                    array[i]=array[i]^array[key];
                    array[key]=array[key]^array[i];
                    key=i;
                    break;
                }
             i++;
            }
            if(i==j)
            {
             if(key-1>0)
             do_quick(array,start,key-1);
                if(key+1<array.length-1)
                    do_quick(array,key+1,end);
                return;
            }
        }

}
}

import java.util.Scanner;
public class DoubleSort {
public static void main(String args[])
{
Scanner scan=new Scanner(System.in);
String s=scan.nextLine();
String[] str=s.split(" ");
double[] array=new double[str.length];
for(int i=0;i<str.length;i++)
array[i]=Double.parseDouble(str[i]);
do_quick(array,0,array.length-1);
for(int i=0;i<array.length;i++)
System.out.print(array[i]+" ");
}
static void do_quick(double[] array,int start,int end)
{
if(start==end)
return;
int key =start;
int i=start,j=end;
        while(i<end || j>start)
        {
         while(i!=j)
            {
         if(array[key]>array[j])
                {
         double tmp=array[key];
         array[key]=array[j];
         array[j]=tmp;
                    key=j; 
                    break;
                 }
                 j--;
            }
            while(i!=j)
            {
             if(array[key]<array[i])
                {
             double tmp=array[key];
             array[key]=array[i];
             array[i]=tmp;
                    key=i;
                    break;
                }
             i++;
            }
            if(i==j)
            {
             if(key-1>0)
             do_quick(array,start,key-1);
                if(key+1<array.length-1)
                    do_quick(array,key+1,end);
                return;
            }
        }

}
}

第四题：

import java.util.Scanner;
public class fac {
public static void main(String args[])
{
Scanner scan=new Scanner(System.in);
int n=scan.nextInt();
solution(n);
}
public static void solution(int n)
{
int result=1;
for(int i=1;i<=n;i++)
result*=i;
System.out.println(result);
}
}

第五题：

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
public class triangle {
public static void main(String args[])
{
Scanner scan=new Scanner(System.in);
String s=scan.nextLine();
String[] str=s.split(" ");
ArrayList<Double> list=new ArrayList<Double>();
for(String k:str)
list.add(Double.parseDouble(k));
if(isTriangle(list))
System.out.println(area(list));
}
public static boolean isTriangle(ArrayList<Double> list)
{
if(list.size()>3) return false;
Collections.sort(list);
return (list.get(0)+list.get(1)>list.get(2))?true:false;
}
public static double area(ArrayList<Double> list)
{
double result=0;
double p=0;
for(double i:list)
p+=i;
p=p/2;
result=Math.sqrt(p*(p-list.get(0))*(p-list.get(1))*(p-list.get(2)));
return result;
}
}

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