public class Demo1 {
    
    
    public static void main(String[] args) {
    
    
        int a = 10;
        int b = 20;
        System.out.println(""+a+b);//输出的是1020
        System.out.println(a+b+"");//输出的是30
        byte c = 10;
      //c = c+1;编译错误，Required type:byte,Provided:int
        c +=1; //相当于c=(byte)(c+1)
        System.out.println(c);//输出的是11
    }
}