Java Basic- Tổng hợp bài tập ôn luyện ngoại lên trong java - Exception in java

#Bai1.java

/*
 * Click nbfs://nbhost/SystemFileSystem/Templates/Licenses/license-default.txt to change this license
 * Click nbfs://nbhost/SystemFileSystem/Templates/Classes/Class.java to edit this template
 */
package bt984;

import java.util.Scanner;

/**
 *
 * @author DiepTV
 */
public class Bai1 {
    public static void main(String[] args) {
        //Khai bao 2 so thuc
        float a = 0, b = 0;
        //Khai bao bien nhap du lieu
        Scanner input = new Scanner(System.in);
        
        System.out.println("Nhap a = ");
        for(;;) {
            try {
                a = Float.parseFloat(input.nextLine());
                break;
            } catch(Exception e) {
//                e.printStackTrace();
//                System.out.println(e.getMessage());
                System.out.println("Nhap lai a = ");
            }
        }
        
        System.out.println("Nhap b = ");
        for(;;) {
            try {
                b = Float.parseFloat(input.nextLine());
                break;
            } catch(Exception e) {
                System.out.println("Nhap lai b = ");
            }
        }
        
        float s = a / b;
        System.out.println("s = " + s);
    }
}

#Bai2.java

/*
 * Click nbfs://nbhost/SystemFileSystem/Templates/Licenses/license-default.txt to change this license
 * Click nbfs://nbhost/SystemFileSystem/Templates/Classes/Class.java to edit this template
 */
package bt984;

import java.util.ArrayList;
import java.util.Scanner;

/**
 *
 * @author DiepTV
 */
public class Bai2 {
    public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<>();
        
        Scanner scan = new Scanner(System.in);
        
        System.out.println("Nhap so phan tu N = ");
        int n = Integer.parseInt(scan.nextLine());
        
        for (int i = 0; i < n; i++) {
            System.out.println("Nhap phan tu list[" + i + "] = ");
            int v = Integer.parseInt(scan.nextLine());
            if(v == 100) {
                break;
            }
            list.add(v);
        }
        
        System.out.println("Danh sach phan tu: ");
        for (Integer v : list) {
            System.out.println(v);
        }
    }
}

Test - Tìm kiếm chuỗi trong chuỗi

#Bai3.java

/*
 * Click nbfs://nbhost/SystemFileSystem/Templates/Licenses/license-default.txt to change this license
 * Click nbfs://nbhost/SystemFileSystem/Templates/Classes/Class.java to edit this template
 */
package bt984;

import java.util.ArrayList;
import java.util.Scanner;

/**
 *
 * @author DiepTV
 */
public class Bai3 {
    public static void main(String[] args) {
        String sourceStr, searchingStr;
        ArrayList<Integer> list = new ArrayList<>();
        
        Scanner scan = new Scanner(System.in);
        
        System.out.println("Nhap chuoi nguon: ");
        sourceStr = scan.nextLine();
        
        System.out.println("Nhap chuoi tim kiem: ");
        searchingStr = scan.nextLine();
        
        int len1 = sourceStr.length(), len2 = searchingStr.length();
        
        if(len2 > len1) {
            System.out.println("Khong tim thay " + searchingStr + " trong " + sourceStr);
        } else {
            for (int i = 0; i <= len1 - len2; i++) {
                //sourceStr = 1234567, sourceStr.charAt(1) -> 2, charAt(4) -> 5
                // Cach 1
//                boolean isEqual = true;
//                for (int j = 0; j < len2; j++) {
//                    if(sourceStr.charAt(i + j) != searchingStr.charAt(j)) {
//                        isEqual = false;
//                        break;
//                    }
//                }
//                if(isEqual) {
//                    list.add(i);
//                    System.out.println("Vi tri tim thay: " + i);
//                }
                // Cach 2
                //searchingStr = 23 -> len2 = 2
                //sourceStr = 1234567, i = 1 -> 1 + 2 (3)
                //t1 = sourceStr.substring(1, 3) -> 23
                //t = sourceStr..substring(2, 4) -> 34
                //String t1 = sourceStr.substring(i, i + len2);
                //t.compareTo(searchingStr) -> t = 34 & 23 -> #0
                //t.compareTo(searchingStr) -> t = 23 & 23 -> =0
                
                if(sourceStr.substring(i, i + len2).compareTo(searchingStr) == 0) {
                    System.out.println("Vi tri tim thay: " + i);
                }
            }
        }
    }
}