JAVA有參無參初始化區別,程序舉例
package JAVA_Project_01_02;
import java.math.BigInteger;
import java.util.ArrayList;
public class TextFactorial {
public static int simpleCircle(int num){
int sum=1;
if (num<0){
throw new IllegalArgumentException("必須爲正整數!");
}
for (int i=1;i<=num;i++){
sum*=i;
}
return sum;
}
public static int recursion(int num){
int sum=1;
if (num<0)
throw new IllegalArgumentException("必須爲正整數!");
if (num==1){
return 1;
}else {
sum=num*recursion(num-1);
return sum;
}
}
public static long addArray(int num){
long[] arr=new long[21];
arr[0]=1;
int last=0;
if (num>=arr.length){
throw new IllegalArgumentException("傳入的值太大");
}
if (num<0)
throw new IllegalArgumentException("必須爲正整數!");
while (last<num){
arr[last+1]=arr[last]*(last+1);
last++;
}
return arr[num];
}
public static synchronized BigInteger bigNumber(int num){
ArrayList list=new ArrayList();
list.add(BigInteger.valueOf(1));
for (int i=list.size();i<=num;i++){
BigInteger lastfact=(BigInteger)list.get(i-1);
BigInteger nextfact=lastfact.multiply(BigInteger.valueOf(i));
list.add(nextfact);
}
return(BigInteger)list.get(num);
}
public static void main(String[] args) {
int num=5;
int num1=23;
System.out.println("簡單的循環計算"+num+"的階乘爲"+simpleCircle(num));
System.out.println("利用遞歸計算"+num+"的階乘爲"+recursion(num));
System.out.println("數組添加計算"+num+"的階乘爲"+addArray(num));
System.out.println("利用BigInteger類計算"+num1+"的階乘爲"+bigNumber(num1));
}
}