java练习本(2019-07-05)

public class Test {
   public static void main(String[] args) {
       int num1 = 0;
       int num2 = 0;
       int sum = 0;
       for(int i = 0; i<3; i++){
           num1 = num1++;
           num2 = ++num2;
           sum += num1 * num2;
      }
       System.out.println(sum);
  }
}

String str1 = new String("hello");
String str2 = new String("hello");
String str3 = "hello";
String str4 = "he" + "llo";
String str5 = "he";
String str6 = "llo";