java平常問題和技巧

1.BigDecimal與int相互轉換：

 1 import java.math.BigDecimal;
 2 public class HelloWorld {
 3     public static void main(String []args) {
 4         //BigDecimal轉int
 5            BigDecimal bigCount =  new BigDecimal("123");
 6         System.out.println(bigCount);
 7         int count = bigCount.intValue();
 8         System.out.println(count);
 9         //int轉BigDecimal
10         int count2 = 456;
11         System.out.println(count2);
12         BigDecimal bigCount2 = new BigDecimal(count2);
13         System.out.println(bigCount2);
14     }
15 }

 2.判斷某元素是否在數組中

1     public boolean isHave(String[] args, String e) {
2         boolean result = false;
3         return Arrays.asList(args).contains(e);
4     }

 這裏的List類型是java.util.Arrays$ArrayList

3.求兩個List並集

1 public List ListUnion(List list1, List list2) {
2     list1.removeAll(list2);
3     list1.addAll(list2);
4     return list1;
5 }