目录
- 顺序执行
- 怎么能多买几个热包子?用 if-else
- 增强寻找可以被整除的程序
- if-else 的嵌套
- if-else 的简化
1. 顺序执行
- 代码块的执行是顺序执行
- 只要程序运行过程中不出错,就会一行行的向下顺序执行
2. 怎么能多买几个热包子?用 if-else
- 买包子的问题
- 买 3 个肉包子
- 如果是刚出笼的热肉包子,就多买两个呢?
- if-else 语法
- if-else 语法,只有一个语句块被执行
- if 和 else 都是 Java 中的关键字
- if 语法
- 把 if-else 看做一个表达式,程序整体还是顺序执行的
- 使用 if-else 来多买两个肉包子
if (boolean 值) {
if 语句块
} else {
else 语句块
}
public class Baozi {
public static void main(String[] args) {
int baozi = 3;
System.out.println("买了" + baozi + "个肉包子");
// 买了3个肉包子
}
}
public class IfElseBaozi {
public static void main(String[] args) {
int baozi = 3;
boolean baoziGangchuLong = true;
if (baoziGangchuLong) {
baozi = baozi + 2;
System.out.println("包子刚刚出笼,买了" + baozi + "个肉包子");
// 包子刚刚出笼,买了5个肉包子
} else {
System.out.println("买了" + baozi + "个肉包子");
}
}
}
3. 增强寻找可以被整除的程序
- 增强点
- 只输出可以整除的数
- 输出商
public class FindDiv {
public static void main(String[] args) {
int a = 35;
int b = 9;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
if (a % b == 0) {
System.out.println(a + "可以整除" + b + "。商为" + (a / b));
}
a++;
}
}
36可以整除9。商为4
45可以整除9。商为5
54可以整除9。商为6
63可以整除9。商为7
72可以整除9。商为8
81可以整除9。商为9
90可以整除9。商为10
99可以整除9。商为11
108可以整除9。商为12
117可以整除9。商为13
126可以整除9。商为14
4. if-else 的嵌套
- 求最大的数
- if-else 就是一个语句,可以是另一个语句的一部分,也可以是 if-else 的一部 分,即嵌套。
- 求 a,b 和 c 三个数的最大数。
public class IfElseNest {
public static void main(String[] args) {
int a = 10;
int b = 99;
int c = 99;
System.out.println("a=" + a + ". b=" + b + ". c=" + c);
if (a == b && b == c) {
System.out.println("a,b和c三个数等大。");
} else {
if (a > b) {
if (a > c) {
System.out.println("a是最大的数。");
} else {
if (a == c) {
System.out.printf("a和c等大。");
} else {
System.out.println("c是最大的数。");
}
}
} else {
if (b > c) {
if (b == a) {
System.out.println("a和b是等大的数。");
} else {
System.out.println("b是最大的数。");
}
} else {
if (b == c) {
System.out.println("b和c等大。");
} else {
System.out.println("c是最大的数。");
}
}
}
}
}
}
a=10. b=99. c=99
b和c等大。
5. if-else 的简化
- if-else 省略大括号
- 如果 if 或者 else 的语句块只有一个语句,可以省略大括号
- 简化求最大数的程序
if (boolean 值)
if 语句块
else
else 语句块
if (boolean 值) {
if 语句块
} else if () {
if 语句块
} else {
else 语句块
}
public class OneStatementIfEles {
public static void main(String[] args) {
int a = 10;
System.out.println("省略大括号");
if (a > 0)
System.out.println("a大于0");
else
System.out.printf("a小于等于0");
System.out.println("比较大小的完整的写法");
if (a > 0) {
System.out.println("a大于0");
} else {
if (a == 0) {
System.out.println("a等于0");
} else {
System.out.println("a小于0");
}
}
System.out.println("比较大小的省略所有大括号的方法");
if (a > 0)
System.out.println("a大于0");
else if (a == 0)
System.out.println("a等于0");
else
System.out.println("a小于0");
System.out.println("比较大小的代码块有多个语句的最优写法");
if (a > 0) {
System.out.println("a大于0");
System.out.printf("买" + a + "个肉包子");
} else if (a == 0) {
System.out.println("a等于0");
System.out.printf("不买肉包子了!");
} else {
System.out.println("a小于0");
System.out.println("肉包子吃多了!");
}
}
}
省略大括号
a大于0
比较大小的完整的写法
a大于0
比较大小的省略所有大括号的方法
a大于0
比较大小的代码块有多个语句的最优写法
a大于0
public class SimpleIfElse {
public static void main(String[] args) {
boolean condition = true;
if (condition) {
System.out.println("condition的值为真");
} else {
System.out.printf("condition的值为假");
}
int a = 10;
int b = 20;
if (a < b) {
System.out.println("a的值为" + a + ", b的值为" + b + ". a<b是真的");
}
System.out.println("如论如何都会执行到");
}
}
condition的值为真
a的值为10, b的值为20. a<b是真的
如论如何都会执行到
6. 补充
/*
* @Author: AI悦创
* @Date: 2020-09-26 15:10:16
* @Last Modified by: aiyuechuang
* @Last Modified time: 2020-09-26 15:26:25
*/
public class Example {
public static void main(String[] args) {
// int a = 10;
// int b = 99;
// int c = 99;
int a, b, c = 10;
System.out.println(a);
}
}
Example.java:13: 错误: 可能尚未初始化变量a
System.out.println(a);
^
1 个错误
你只能这样声明赋值:
int a = 10, b = 99, c = 99;