各数据类型互转

Long与Integer之间的转换

Integer a = 10;
Long b = a.longValue();

Long a = 10L;
Integer b = a.intValue();

　long longValue = 123456L;
　int intValue = (int) longValue;

String与Iong之间的转换

long l2 = 2;
String s2 = String.valueOf(l2);

String s1 = "123";
Long L = Long.parseLong(s1);

String s2 = "12";
long l = Long.ValueOf(s2);

String与Integer之间的转换

int number = 10;
String s2 = String.valueOf(number);

String s = "100";
int x = Integer.parseInt(s);

String[]与String之间的转换

String a = "111,222,333,444";
String[] b = a.split(",");

String[] a = new String[]{"111","222","333"};
String temp = Arrays.toString(a); //在执行此行代码的时候，会从第二个开始在每个元素前面加上空格，可参照Arrays.toString()方法，将空格replace掉即可。
String s = temp.substring(1,temp.length()-1);

String[]与List之间的转换

String str = "a,b,c";
List<String> list1 = Arrays.asList(str.split(",")); //[a, b, c]

List<String> list = new ArrayList<String>();
list.add("a");
list.add("b");
list.add("c");
String str1 = StringUtils.join(list, ","); //a,b,c

BigDecimal与Long、int之间的转换

int i = 123;
BigDecimal b = new BigDecimal(i);

Long l = 123L;
BigDecimal b = new BigDecimal(l);

BigDecimal c = new BigDecimal(b);
Long l = c.longValue();

BigDecimal c = new BigDecimal(b);
int i = c.intValue();

String数组转为List各种格式

public static final String SEGMENTATION = ",";

/**
 * 将String 转换成 List<Long>
 *
 * @param str
 * @return
 */
public static List<Long> splitStrToListLong(String str) {
	List<Long> list = new ArrayList<>();
	if (StringUtils.isNotEmpty(str)) {
		String[] split = StringUtils.split(str, SEGMENTATION);
		for (String string : split) {
			list.add(NumberUtils.toLong(string, -1l));
		}
	}
	return list;
}

/**
 * 将String 转换成 List<Integer>
 *
 * @param str
 * @return
 */
public static List<Integer> splitStrToListInt(String str) {
	List<Integer> list = new ArrayList<>();
	if (StringUtils.isNotEmpty(str)) {
		String[] split = StringUtils.split(str, SEGMENTATION);
		for (String string : split) {
			list.add(NumberUtils.toInt(string, -1));
		}
	}
	return list;
}

/**
 * 将String 转换成 List<String>
 *
 * @param str
 * @return
 */
public static List<String> splitStrToListString(String str) {
	List<String> list = new ArrayList<>();
	if (StringUtils.isNotEmpty(str)) {
		String[] split = StringUtils.split(str, SEGMENTATION);
		//参数中只有一个值
		 if(split == null){
			list.add(str);
			return list ;
		}
		for (String string : split) {
			list.add(string);
		}
	}
	return list;
}

/**
 * list<String>转string
 * @param list
 * @param separator
 * @return
 */
public static String listToString(List list, char separator) {
	StringBuilder sb = new StringBuilder();
	for (int i = 0; i < list.size(); i++) {
		sb.append(list.get(i)).append(separator);
	}
	return sb.toString().substring(0, sb.toString().length() - 1);
}