Java 将空值设置为整数
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Setting null value to integer
提问by Vijay Kumar
How can i set null to integer variable initially instead of "0". I know already by default all int value is "0". I used String.valueOf()method etc. I dont want to print as "null". I want to print blank like " ". I get number format exception. Please give one solution for that.
我如何最初将 null 设置为整数变量而不是“0”。我已经知道默认情况下所有 int 值都是“0”。我使用了String.valueOf()方法等。我不想打印为“null”。我想像“”一样打印空白。我得到数字格式异常。请给出一个解决方案。
Thanks in advance
提前致谢
Here is the code
这是代码
public class IntegerDemo {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
String id="";
System.out.println(""+Integer.parseInt(id));
}
}
采纳答案by dharam
I am sure you are over-complicating the problem, it is a real simple thing to do. Check the code below:
我相信你把问题复杂化了，这是一件非常简单的事情。检查下面的代码：
Integer i = null;
System.out.println(i == null ?"":i);
回答by Suresh Atta
回答by inteloid
Integer int = null;
ints are primitives, they have default values different from null.
int 是基元，它们的默认值与 null 不同。
回答by ced-b
You would have to stick with the java.lang.Integerclass.
你必须坚持java.lang.Integer上课。
String id = ""
Integer test = null;
if (!"".equals(id))
{
test = Integer.parseInt(id);
}
回答by Makoto
Creating an instance of Integerwith its primary value as nullis meaningless, but you can do this on declaration:
Integer使用其主要值创建一个实例null是没有意义的，但您可以在声明时执行此操作：
Integer id = null;
The reason you're getting NumberFormatExceptionis laid out in the documentation:
你得到的原因在文档中NumberFormatException列出：
An exception of type NumberFormatException is thrown if any of the following situations occurs:
The first argument is null or is a string of length zero.
The radix is either smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX.
Any character of the string is not a digit of the specified radix, except that the first > character may be a minus sign '-' ('\u002D') or plus sign '+' ('\u002B') provided that the string is longer than length 1.
The value represented by the string is not a value of type int.
如果发生以下任何一种情况，则会抛出 NumberFormatException 类型的异常：
第一个参数为 null 或长度为零的字符串。
基数小于 Character.MIN_RADIX 或大于 Character.MAX_RADIX。
字符串的任何字符都不是指定基数的数字，除了第一个 > 字符可以是减号 '-' ('\u002D') 或加号 '+' ('\u002B') 前提是字符串比长度 1 长。
字符串表示的值不是 int 类型的值。
You can't call Integer.parseInt("")or Integer.parseInt(null), with that limitation.
你不能调用Integer.parseInt("")or Integer.parseInt(null)，有这个限制。
回答by azz
The simple boxed Integer Integer i = null;has already been supplied. Here is an alternative:
Integer i = null;已经提供了简单的盒装整数。这是一个替代方案：
class NullableInt {
private int value;
private boolean isNull;
public NullableInt() { isNull = true; }
public NullableInt(int value) {
this.value = value;
isNull = false;
}
public NullableInt(String intRep) {
try { value = Integer.parseInt(intRep);
} catch (NumberFormatException) {
isNull = true;
}
}
boolean isNull() { return isNull; }
void setNull(boolean toNull) { isNull = toNull; }
void setValue(int value) { this.value = value; }
int getValue() { return value; }
@Override
public String toString() { return isNull ? "" : value; }
}
NullableInt integer1 = new NullableInt(56);
NullableInt integer2 = new NullableInt();
System.out.pritnln(integer1); // >> "56"
System.out.println(integer2); // >> ""
// and finally, to address the actual question:
String id = "";
System.out.println(new NullableInt(id)); // >> ""
回答by commit
If you parse nullor blankas int it will throw numberFormatException. Check for that before parsing:
如果您解析null或blank作为 int 它将抛出numberFormatException. 在解析之前检查：
try{
System.out.println(StringUtils.isNotBlank(id)?Integer.parseInt(id):"");
}
catch(NumberFormatException e){
System.out.println("Not A Number");
}
Also be sure if string has not number by catching exception. StringUtils.isNotBlank()will check for both nullas well as blank.
还要通过捕获异常来确定字符串是否没有数字。StringUtils.isNotBlank()将检查两者null以及blank.
