本科生java考试练习题目

前言

论文休息时间，帮实验室的师弟师妹做几道java考试题目，预祝师弟师妹考试取得优异成绩

题目

1、创建3个线程，每个线程睡眠一段时间（0-6秒），然后结束

class SleepFun implements Runnable {
private int sleepTime = 0;

public SleepFun(int time) {
this.sleepTime = time * 1000;
}

@Override
public void run() {
try {
Thread.sleep(this.sleepTime);
System.out.println("Hello World!" + this.sleepTime);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}

public class TestThread {
public static void main(String args[]) {
SleepFun f1 = new SleepFun(1);
SleepFun f2 = new SleepFun(3);
SleepFun f3 = new SleepFun(5);

Thread t1 = new Thread(f1);
t1.start();

Thread t2 = new Thread(f2);
t2.start();

Thread t3 = new Thread(f3);
t3.start();
}
}

2、编写一个程序，从键盘读入一个实数，然后检查实数是否小于零，是就抛出异常，否则将这个数开平方

import java.util.Scanner;

public class TestException {
public double sqrtNumber(double num) throws Exception {
if (num >= 0) {
return Math.sqrt(num);
} else {
throw new Exception("This number is less than zero!");
}
}

public static void main(String[] args) {
double num;
Scanner cin = new Scanner(System.in);

while (cin.hasNext()) {
num = cin.nextDouble();

try {
TestException te = new TestException();
double res = te.sqrtNumber(num);
System.out.println(res);
} catch (Exception e) {
e.printStackTrace();
}
}

cin.close();
}
}