##今天的筆記

**Bufferreader:**
使用BufferedReader物件的readLine()方法必須處理java.io.IOException異常(Exception)。
BufferReader讀取的資料都以字串的形式儲存，如果需要其他形式的資料，需要進行強制轉換。

import java.io.*;
    public class Main {
        public static void main(String[] args) throws IOException {
            BufferedReader br1=new BufferedReader(new InputStreamReader(System.in));//建立BufferedReader物件，從鍵盤讀入
            BufferedReader br2= new BufferedReader(new FileReader("test.txt"));//建立BufferedReader物件，從文字檔案讀入        
			String str = br.readLine();  //讀取一行字串  
			int a = Integer.parseInt(str);  //將字元轉化為整型  
			System.out.println(a);  
            String[] temp=br1.readLine().split(" ");//讀取一行資料並用空格分隔，存入字串陣列
        }
    ｝

**##ArrayList:**
提供新增ˋ修改ˋ刪除等....

package beginnersbook.com;
import java.util.ArrayList;
public class GetMethodExample {
   public static void main(String[] args) {
       ArrayList<String> al = new ArrayList<String>();
       al.add("pen");
       al.add("pencil");
       al.add("ink");
       al.add("notebook");
       al.add("book");
       al.add("books");
       al.add("paper");
       al.add("white board");

       System.out.println("First element of the ArrayList: "+al.get(0));
       System.out.println("Third element of the ArrayList: "+al.get(2));
       System.out.println("Sixth element of the ArrayList: "+al.get(5));
       System.out.println("Fourth element of the ArrayList: "+al.get(3));
   }
}

**length**:
Arrays (int[], double[], String[]) — 取得Array的長度
**length()**:
String related Object (String, StringBuilder, etc) — 取得字串的長度
**size():**
Collection Object (ArrayList, Set, etc) — 取得集合物件相關大小

import java.util.*;
public class HelloWorld{

     public static void main(String []args){
      
        String[] arr = {"a", "b", "c"};
        String s = "123456";
        Set<String> set = new HashSet();
        set.add("example");
        
        System.out.println(arr.length); //3
        System.out.println(s.length()); //6
        System.out.println(set.size()); //1
     }
}