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BookDemo.java
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98 lines (89 loc) · 2.28 KB
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import java.io.FileNotFoundException;
import java.io.PrintStream;
/**
* @author wenci
* @date: 2017/11/30
* @description:
*/
public class BookDemo {
static long factorial = 1;
public static void main(String[] args) {
// System.out.println("this is normal");
// System.err.println("this is error manually");
// variableExchange();
judgeMounth(6);
// long result = multiply(5);
// System.out.println(result);
// selectSort(20);
}
/**
* 实现一个数的阶乘，递归方式
* @param num
* @return
*/
private static long multiply(int num) {
if (num < 1) {
return factorial;
}
factorial = factorial * num--;
return multiply(num);
}
/**
* @param mounth 当switch-case语句没有break时会一起执行到break的地方
*/
private static void judgeMounth(int mounth) {
switch (mounth) {
case 12:
case 1:
case 2:
System.out.println("" + mounth + " 是冬季");
break;
case 3:
case 4:
case 5:
System.out.println("" + mounth + " 是春季");
break;
case 6:
case 7:
case 8:
System.out.println("" + mounth + " 是夏季");
break;
case 9:
case 10:
case 11:
System.out.println("" + mounth + " 是秋季");
break;
}
}
/**
* 利用 System.setOut setErr setIn 改变输出输入流。
*/
private static void redirectOutputStream() {
PrintStream outer = System.out;
try {
PrintStream ps = new PrintStream("log.txt");
System.setOut(ps);
int age = 18;
System.out.println("年龄设置成功");
String sex = "女";
System.out.println("性别设置成功");
System.out.println(String.format("这是个%s孩子，今年%d岁了。", sex, age));
System.setOut(outer);
System.out.println("运行完毕，请查看日志");
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
/**
* 不使用第三个变量实现两数字互换
*/
private static void variableExchange() {
long a = 5569, b = 9965;
System.out.println(String.format("a=%d, b=%d", a, b));
System.out.println("after exchange:");
a = a ^ b;
b = b ^ a;
a = a ^ b;
System.out.println(String.format("a=%d, b=%d", a, b));
}
}