JAVA算法大全之判断101-200之间有多少个素数，并输出所有素数。程序分析：判断素数的方法：用一个数分别去除2到sqrt(这个数)，如果能被整除， 则表明此数不是素数，反之是素数。
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
public class Basic2 {
public static void main(String args[])
{
Basic2 my = new Basic2();
my.outputSushu();
}
public void outputSushu()
{
int startNum = 0 ;
int endNum = 0;
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println(“请输入起始数”);
try {
startNum = Integer.parseInt(br.readLine());
} catch (NumberFormatException e) {
// TODO Auto-generated catch block
outputSushu();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(“请输入结束数”);
try {
endNum = Integer.parseInt(br.readLine());
} catch (NumberFormatException e) {
// TODO Auto-generated catch block
outputSushu();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(startNum<=endNum)
{
ArrayList<Integer> sushu = new ArrayList<Integer>();
for(int i = startNum;i<= endNum;i++)
{ boolean flag = true;
for(int j = 2; j <=Math.sqrt(i) ; j++)
{
if ((i % j)== 0 )
{
flag = false;
}
}
if (flag)
{
sushu.add(i);
}
}
if(sushu.size()>0)
{
System.out.print(startNum+”与”+endNum+”之间的素数有”+sushu.size()+”个,包括”);
for( int m :sushu)
{
System.out.print(m+” “);
}
System.out.println();
}
}
else{
outputSushu();
}
outputSushu();
}
}
运行结果如下图