Source Code Bài Học

/*
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 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package lession6;

/**
 *
 * @author Diep.Tran
 */
public class Main {
    public static void main(String[] args) {
        //String => ham trong string
        String str = "Hello";
        int x = 5;//kieu du lieu
        float y = 6.5f;//kieu du lieu
        
        System.out.println("Length : " + str.length());
        char c = str.charAt(0);
        System.out.println("Index 0 : " + c);
        //thuc hien qua trinh noi chuoi
        str = str.concat(" World!!!");
        System.out.println("new str : " + str);
        
        System.out.println("A".compareTo("B"));
        
        String str1 = "123456123456";
        String search = "2";
        System.out.println("Index : " + str1.indexOf(search));
        System.out.println("Index : " + str1.lastIndexOf(search));
        
        String[] params = str1.split("23");
        System.out.println("=========== Ket qua cat chuoi ==============");
        for (String param : params) {
            System.out.println(param);
        }
        
        //cac cach khai bao chuoi (quan ly) string trong java
        //1 chuong >> danh sach chuoi dc nhap vao tu ban
        //StringBuilder & StringBuffer => chuoi + ky => noi chuoi lai
        //Cach dung
        StringBuilder builder = new StringBuilder();
        builder.append("Hello");
        builder.append(" World");
        builder.append('!');
        builder.append('!');
        builder.append('!');
        
        System.out.println(builder.toString());
        
        StringBuffer buffer = new StringBuffer();
        buffer.append("Hello");
        buffer.append(" World");
        buffer.append('!');
        buffer.append('!');
        buffer.append('!');
        
        System.out.println(buffer.toString());
        //giai thich cho cac ban giong va khac nhau StringBuilder & StringBuffer
        //5 tim hieu tren mang => 
    }
}

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package lession6;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.Vector;

/**
 *
 * @author Diep.Tran
 */
public class Test {
    public static void main(String[] args) {
        //Collections => nhieu hon.
        //Array
        int[] arr1 = new int[5];
        float[] arr2 = new float[10];
        //length (arr1.length), index : 0 => length - 1
        arr1[0] = 12;
        arr1[1] = 21;
//        arr1[5] = 10;//bug thong dung => ko quen => tim bug nhanh
        for (int i = 0; i < arr1.length; i++) {
            System.out.println("Nhap du lieu");
            System.out.println("Duyet cac phan tu trong mang");
        }
        //tao 1 mang gom N phan tu => N dc nhap tu ban phim => tinh tong cac so chia het cho 3 trong mang
        Scanner scanner = new Scanner(System.in);
        System.out.println("Nhap cac phan tu trong mang: ");
        int n;
        n = scanner.nextInt();
        int[] list = new int[n];//so phan tu cua mang => xac dinh dc
        
        for (int i = 0; i < n; i++) {
            System.out.format("\nNhap list[%d] = ", i);
            list[i] = scanner.nextInt();
        }
        
        int total = 0;
        for (int i = 0; i < n; i++) {
            if(list[i] % 3 == 0) {
                total += list[i];
            }
        }
        System.out.println("Total: " + total);
        
        //Collections => quan ly dc mang => du lieu dong => Collections
        //List
        List<Integer> list1 = new ArrayList<>();
        //them phan tu
        list1.add(12);
        list1.add(343);
        list1.add(234);
        list1.add(234);
        list1.add(123);
        
        //xoa 1 phan tu khoi mang
        list1.remove(1);
        
        //duyet qua cac phan tu trong mang
        for (Integer integer : list1) {
            System.out.println(integer);
        }
        
        //Vector
        list1 = new Vector<>();
        //them phan tu
        list1.add(12);
        list1.add(343);
        list1.add(234);
        list1.add(234);
        list1.add(123);
        
        //xoa 1 phan tu khoi mang
        list1.remove(1);
        
        //duyet qua cac phan tu trong mang
        for (Integer integer : list1) {
            System.out.println(integer);
        }
    }
}