第1关 

两整数的四则运算

package step1;import java.util.Scanner;public class Arithmetic2Num {public static void main(String[] args) {
// ---------------------Begin------------------------Scanner sc=new Scanner(System.in);int a=sc.nextInt();int b=sc.nextInt();System.out.print("a+b=");System.out.println(a+b);System.out.print("a*b=");System.out.println(a*b);System.out.print("a-b=");System.out.println(a-b);System.out.print("a/b=");System.out.println(a/b);// ---------------------End------------------------}
}

第2关 打印三角形

package step2;import java.util.Scanner;public class PosTriangle {public static  void prin(int n,int n2){int num=n*2-1;if(n==1){for(int i=0;i<n2;i++)System.out.print(' ');System.out.println('*');return;}prin(n-1,n2+1);for(int i=0;i<n2;i++)System.out.print(' ');for(int i=0;i<num;i++)System.out.print('*');System.out.println();}public static void main(String[] args) {Scanner scanner = new Scanner(System.in);//定义输入的行数:int n = scanner.nextInt();// ---------------------Begin------------------------          prin(n,0);// ---------------------End------------------------}
}

第3关 循环之倒三角形

package step3;import java.util.Scanner;public class NegTriangle {public static  void prin(int n,int x){int num=n*2-1;if(n==x){for(int i=0;i<num;i++)System.out.print('*');System.out.println();return;}prin(n+1,x);for(int i=0;i<x-n;i++)System.out.print(' ');for(int i=0;i<num;i++)System.out.print('*');System.out.println();}public static void main(String[] args) {Scanner scanner = new Scanner(System.in);//定义输入的行数:int n = scanner.nextInt();// ---------------------Begin------------------------prin(1,n);// ---------------------End------------------------}
}

第4关 水仙花数

package step4;import java.util.Scanner;public class narcissisticNumber {public static boolean dfs(int x){int sum=0;int num=x;while(num!=0){int m=num%10;sum=sum+(m*m*m);if(sum>x)return false;      num=num/10;}if(sum==x) return true;else return false;}public static void main(String[] args) {Scanner scanner = new Scanner(System.in);//获取起始范围int i = scanner.nextInt();//获取终止范围int j = scanner.nextInt();// ---------------------Begin------------------------int l=0;for(int k=i;k<=j;k++){ if(dfs(k))System.out.println(k);else l++;}if(l==(j-i+1)){System.out.print(i);System.out.print('~');System.out.print(j);System.out.println("范围内无水仙花数！");}// ---------------------End------------------------}
}

第5关 a与b之间的素数

package step5;import java.util.Scanner;public class PrimeNumber {public static boolean find(int x){if(x==1)return false;for(int i=2;i<=9;i++){if(x%i==0&&i<x)return false;}return true;}public static void main(String[] args) {Scanner scan = new Scanner(System.in);// ---------------------Begin------------------------int i = scan.nextInt();int j = scan.nextInt();System.out.print(i);System.out.print("到");System.out.print(j);System.out.println("之间的素数有：");for(int k=i;k<=j;k++){if(find(k)){ System.out.print(k);System.out.print(' ');}}}// ---------------------End------------------------}

第6关 

余X的整数

package step6;import java.util.Scanner;public class LeftXnumber {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);// ---------------------Begin------------------------int a=scanner.nextInt();int b=scanner.nextInt();int c=scanner.nextInt();for(int i=a;i<=b;i++){if(i%c==0)System.out.println(i);}// ---------------------End------------------------}
}

第7关 求解1元2次方程

package step7;import java.util.Scanner;public class SolveEquations {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);double a=scanner.nextDouble();double b=scanner.nextDouble();double c=scanner.nextDouble();double delta=b*b-4*a*c;if(delta>0){double x1=(-b+Math.sqrt(delta))/(2*a);double x2=(-b-Math.sqrt(delta))/(2*a);System.out.printf("方程有两个解：x1=%.2f x2=%.2f",x1,x2);}else if(delta==0){double x=-b/(2*a);System.out.printf("方程有一个解：x1=x2=&.2f",x);}else {System.out.println("此方程无解");}// ---------------------End------------------------// ---------------------End------------------------}
}