一、基本程序执行
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* hello,world *
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二、数据类型和变量和基本运算符
Scanner scanner = new Scanner(System.in);
int i = scanner.nextInt();
System.out.println(i / 100 * 100);
三、逻辑判断语句
Scanner sc = new Scanner(System.in);
int year = sc.nextInt();
int month = sc.nextInt();
int day = sc.nextInt();
int sum = 0;// 总天数
switch (month) {/* 先计算某月以前月份的总天数 */
case 1:
sum = 0;
break;
case 2:
sum = 31;
break;
case 3:
sum = 59;
break;
case 4:
sum = 90;
break;
case 5:
sum = 120;
break;
case 6:
sum = 151;
break;
case 7:
sum = 181;
break;
case 8:
sum = 212;
break;
case 9:
sum = 243;
break;
case 10:
sum = 273;
break;
case 11:
sum = 304;
break;
case 12:
sum = 334;
break;
default:
System.out.println(“日期错误“);
break;
}
sum = sum + day;/* 再加上某天的天数 */
if (year % 400 == 0 || year % 4 == 0 && year % 100 != 0 && month > 2) {
sum ++;
}
System.out.println(“第” + sum + “天“);
四、循环语句练习
int i=1,j=1;
while (i <= 9){
System.out.print(i + “*” + j + “=” + i * j + “\t”);
j ++;
if (j > i){
j = 1;
i ++;
System.out.println();
}
}
int j = 1,k = 1;//控制换行
for (int i = 1;i <= 15;i ++){
System.out.print(i + “\t”);
j ++;
if (j > k){
j = 1;
k ++;
System.out.println();
}
}
for (int j = 1;j <= 8;j ++){
if ( (i + j) % 2 == 0)
System.out.print(“■”);
else
System.out.print(” “);
}
System.out.println();
}
int day = 9; //第九天
int x1 = 1; //当前的桃子
int x2;//前一天的桃子
for (int i = day;i >= 1;i –){
x2 = (x1 + 1) * 2;
x1 = x2;
System.out.println(“第” + i + “天的桃子个数：” + x2);
}
五、数组练习
（别忘了二维数组排序）