第一题：
import java.util.Scannerpublic class sqr {
public static void main(String args[])
{
Scanner scan=new Scanner(System.in)
int num=scan.nextInt()
int result=0
for(int i=1i<=numi++)
result+=i*i
System.out.println("result is: "+result)
}
}
第二题：
import java.util.Scannerclass prime
{
public static void main(String args[])
{
Scanner scan=new Scanner(System.in)
int num=scan.nextInt()
for(int i=1i<=numi++)
if(isPrime(i)) System.out.print(i+" ")
}
public static boolean isPrime(int val)
{
for(int i=2i<vali++)
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=0i<str.lengthi++)
array[i]=Integer.parseInt(str[i])
do_quick(array,0,array.length-1)
for(int i=0i<array.lengthi++)
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=0i<str.lengthi++)
array[i]=Double.parseDouble(str[i])
do_quick(array,0,array.length-1)
for(int i=0i<array.lengthi++)
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.Scannerpublic 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=1i<=ni++)
result*=i
System.out.println(result)
}
}
第五题：
import java.util.ArrayListimport 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
}
}
import java.io.BufferedReaderimport java.io.BufferedWriter
import java.io.File
import java.io.FileNotFoundException
import java.io.FileOutputStream
import java.io.IOException
import java.io.InputStreamReader
import java.io.OutputStreamWriter
public class Demo {
public static void main(String[] args) {
System.out.println(求和(1000))
}
/**
* 求从0开始连续整数之和
* @param max 从0开始，一直加到max为止
* @return 和
*/
private static int 求和(int max){
int result = 0
for(int i=0i<=maxi++)
result += i
return result
}
private static void 保存姓名和住址(){
System.out.println("请输入姓名和住址，用逗号隔开。输入‘quit’退出。")
String strInput = null
File file = new File("姓名住址.txt")//建立文件
BufferedReader br = new BufferedReader(new InputStreamReader(System.in))//接收控制台输入
BufferedWriter bw = null
try {
bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file)))//输出到文件
bw.append("姓名\t住址")
bw.newLine()
} catch (FileNotFoundException e1) {
e1.printStackTrace()
} catch (IOException e) {
e.printStackTrace()
}
while(true){
System.out.print("_>")
try {
strInput = br.readLine()
if(strInput.equalsIgnoreCase("quit")){ //不论quit大小写，退出程序
bw.flush()
break
}else{
if(bw != null){
//不论姓名和住址的分隔符是英文逗号还是中文逗号，均替换为制表符，主要是为了输出的美观
bw.append(strInput.replaceFirst("[,，]", "\t"))
bw.newLine()
}
}
} catch (IOException e) {
e.printStackTrace()
}
}
try{
//关闭输入和输出
if(br != null)
br.close()
if(bw != null)
bw.close()
}catch(IOException e){
e.printStackTrace()
}
}
}
import java.util.ArrayListimport java.util.Arrays
import java.util.Collections
public class Homework18_20 {
public static void main(String[] args) {
Integer[] arr1 = {5,1,4,32,8,7,9,-6}
Integer[] arr2 = {5,2,87,10,1}
ArrayList<Integer> ar1 = new ArrayList<Integer>(Arrays.asList(arr1))
System.out.println(ar1)
ArrayList<Integer> ar2 = new ArrayList<Integer>(Arrays.asList(arr2))
ArrayList<Integer> ar12 = new ArrayList<Integer>(Arrays.asList(arr1))
ar12.retainAll(ar2) //ar12获得ar1 和 ar2的交集
System.out.println(ar12)
ar1.removeAll(ar12) //ar1 异或
ar2.removeAll(ar12) //ar2 异或
ArrayList<Integer> ar3 = new ArrayList<Integer>() //新建结果集合
ar3.addAll(ar1) //加入ar1异或
ar3.addAll(ar2) //加入ar2异或
Collections.sort(ar3) //ar3自然排序
for (int i = ar3.size() - 1 i > -1 i--) {
System.out.print(ar3.get(i) + " ") //倒序取出
}
}
}
