Bài tập Java Full HD ko che

import java.util.*;
import java.util.Arrays;
public class Main
{   
    // Ham
    public static boolean laSoNguyenTo(int n){
        if(n < 2) return false;
        for(int i=2;i<=Math.sqrt(n);i++) {
            if(n % i == 0) return false;
        }
        return true;
    }
    
    public static int laSoFib(int n) {
        int f0 = 0;
        int f1 = 1;
        int fn = 1;
 
        if (n < 0) {
            return -1;
        } else if (n == 0 || n == 1) {
            return n;
        } else {
            for (int i = 2; i < n; i++) {
                f0 = f1;
                f1 = fn;
                fn = f0 + f1;
            }
        }
        return fn;
    }
    // Cau 8 den cau 18
    public static void cau8(){
        System.out.print("Nhap n:");
        int n = sc.nextInt();
        
        System.out.println(n+" so nguyen to dau tien la:");
        int sum=0,count=0;
        for(int i=0;i<100;i++){
            if(count==n) break;
            if(laSoNguyenTo(i)){
                count++;
                System.out.print(i+" ");
                sum+=i;
            }
        }
        System.out.println("\nTong "+n+" so nguyen to dau tien la:"+sum);
    }
    
    public static void cau9(){
        System.out.print("Nhap mot chuoi:");
        String str = sc.nextLine();
        int count=0;
        for(int i=0;i<str.length();i++){
            if(str.charAt(i) == 'a') count++;
        }
        System.out.println("So luong chu 'a' trong chuoi la: "+count);
    }
    
    public static void cau10(){
        System.out.print("Nhap mot chuoi:");
        String str = sc.nextLine();
        System.out.println("Chuoi sau khi tach la:");
        int count=1;
        for(int i=0;i<str.length();i++){
            if(str.charAt(i) == ' ') count++;
        }
        String arrStr[] = new String[count];
        arrStr = str.split(" ");
        for(int i=0;i<count;i++){
            System.out.println(arrStr[i]);
        }
    }
    
    public static void cau11(){
        System.out.print("Nhap mot chuoi:");
        String str = sc.nextLine();
        int count=0;
        for(int i=0;i<str.length();i++){
            if(Character.isDigit(str.charAt(i))) count+=1;
        }
        System.out.println("So ky tu la so trong chuoi la:"+count);
    }
    
    public static void cau12(){
        
        int count=0,sum=0;
        System.out.println("Nhap mot day so xen ke bat ky:");
        while(count!=10){
            int n = sc.nextInt();
            if(n%2==0){
                System.out.print(n+" ");
                sum+=n;
                count++;
            }
        }
        System.out.println("\nTong cua 10 so chan dau tien la:"+sum);
    }
    
    public static void cau13(){
        System.out.println("So le tu 1 den 99 la:");
        for(int i=0;i<100;i++){
            if(i%2==1) System.out.print(i+" "); 
        }
    }
    
    public static void cau14(){
        System.out.println("Cac so la boi so cua 7 la:");
        int rs=7,i=1,sum=0;
        while(true){
            rs = 7 * (i++);
            if(rs>100) break;
            sum+=rs;
        }
        System.out.println("\nTong cac so la boi cua 7 (1->100):"+sum);
    }
    
    public static void cau15(){
        System.out.print("Nhap 1 day so:");
        String str = sc.nextLine();
        String myStr[] = str.split(" ");
        int max = Integer.parseInt(myStr[0]);
        int min = Integer.parseInt(myStr[0]);
        for(int i=1;i<myStr.length;i++){
            int num1 = Integer.parseInt(myStr[i]);
            int num2 = Integer.parseInt(myStr[i]);
            if(num1 > max) max = num1;
            if(num2 < min) min = num2;
        }
        System.out.println("Min:"+min+"\nMax:"+max);
    }
    
    public static void cau16(){
        System.out.print("Nhap mot so bat ky:");
        int n = sc.nextInt();
        if(n==0) System.out.println("zero");
        System.out.println(n%2==0?"So chan":"So le");
    }
    
    public static void cau17(){
        System.out.println("Boi cua so 3 (tu 300 den 3):");
        int rs=3,i=1;
        int a[] = new int[100]; //So luong phan tu mac dinh la 100 (tu hieu nha :)) )
        while(true){
            rs = 3*i;
            if(rs>300) break;
            a[i-1] = rs;
            i++;
        }
        for(i=a.length-1;i>=0;i--){
            System.out.print(a[i]+" ");
        }
    }
    
    public static void cau18(){
        System.out.print("Nhap n:");
        int n = sc.nextInt();
        System.out.println(n+" so fib dau tien la");
        int i=1;
        while(i <= n){
            System.out.print(laSoFib(i++)+" ");
        }
    }
    static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		//cau8();
		//cau9();
		//cau10();
		//cau11();
		//cau12();
		//cau13();
		//cau14();
		//cau15();
		//cau16();
		//cau17();
		//cau18();
	}
}