Java 如何在左侧用零填充整数？
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How can I pad an integer with zeros on the left?
提问by Omar Kooheji
How do you left pad an intwith zeros when converting to a Stringin java?
在 java 中int转换为 a 时，如何用零填充 an String？
I'm basically looking to pad out integers up to 9999with leading zeros (e.g. 1 = 0001).
我基本上希望9999用前导零填充整数（例如 1 = 0001）。
采纳答案by Yoni Roit
Use java.lang.String.format(String,Object...)like this:
java.lang.String.format(String,Object...)像这样使用：
String.format("%05d", yournumber);
for zero-padding with a length of 5. For hexadecimal output replace the dwith an xas in "%05x".
用于填充零为5的长度十六进制输出替换d用x如在"%05x"。
The full formatting options are documented as part of java.util.Formatter.
完整的格式选项记录为java.util.Formatter.
回答by Omar Kooheji
Found this example... Will test...
找到这个例子...将测试...
import java.text.DecimalFormat;
class TestingAndQualityAssuranceDepartment
{
public static void main(String [] args)
{
int x=1;
DecimalFormat df = new DecimalFormat("00");
System.out.println(df.format(x));
}
}
Tested this and:
对此进行了测试，并且：
String.format("%05d",number);
Both work, for my purposes I think String.Format is better and more succinct.
两者都有效，就我的目的而言，我认为 String.Format 更好更简洁。
回答by Boris Pavlovi?
If you for any reason use pre 1.5 Java then may try with Apache Commons Lang method
如果您出于任何原因使用 1.5 之前的 Java，则可以尝试使用 Apache Commons Lang 方法
org.apache.commons.lang.StringUtils.leftPad(String str, int size, '0')
回答by johncurrier
public static String zeroPad(long number, int width) {
long wrapAt = (long)Math.pow(10, width);
return String.valueOf(number % wrapAt + wrapAt).substring(1);
}
The only problem with this approach is that it makes you put on your thinking hat to figure out how it works.
这种方法的唯一问题是它会让你戴上思考帽来弄清楚它是如何工作的。
回答by Deepak
Although many of the above approaches are good, but sometimes we need to format integers as well as floats. We can use this, particularly when we need to pad particular number of zeroes on left as well as right of decimal numbers.
虽然上面的很多方法都很好，但有时我们需要格式化整数和浮点数。我们可以使用它，特别是当我们需要在十进制数的左侧和右侧填充特定数量的零时。
import java.text.NumberFormat;
public class NumberFormatMain {
public static void main(String[] args) {
int intNumber = 25;
float floatNumber = 25.546f;
NumberFormat format=NumberFormat.getInstance();
format.setMaximumIntegerDigits(6);
format.setMaximumFractionDigits(6);
format.setMinimumFractionDigits(6);
format.setMinimumIntegerDigits(6);
System.out.println("Formatted Integer : "+format.format(intNumber).replace(",",""));
System.out.println("Formatted Float : "+format.format(floatNumber).replace(",",""));
}
}
回答by Shashi
int x = 1;
System.out.format("%05d",x);
if you want to print the formatted text directly onto the screen.
如果您想将格式化的文本直接打印到屏幕上。
回答by das Keks
If performance is important in your case you could do it yourself with less overhead compared to the String.formatfunction:
如果性能在您的情况下很重要，与String.format函数相比，您可以用更少的开销自己完成：
/**
* @param in The integer value
* @param fill The number of digits to fill
* @return The given value left padded with the given number of digits
*/
public static String lPadZero(int in, int fill){
boolean negative = false;
int value, len = 0;
if(in >= 0){
value = in;
} else {
negative = true;
value = - in;
in = - in;
len ++;
}
if(value == 0){
len = 1;
} else{
for(; value != 0; len ++){
value /= 10;
}
}
StringBuilder sb = new StringBuilder();
if(negative){
sb.append('-');
}
for(int i = fill; i > len; i--){
sb.append('0');
}
sb.append(in);
return sb.toString();
}
Performance
表现
public static void main(String[] args) {
Random rdm;
long start;
// Using own function
rdm = new Random(0);
start = System.nanoTime();
for(int i = 10000000; i != 0; i--){
lPadZero(rdm.nextInt(20000) - 10000, 4);
}
System.out.println("Own function: " + ((System.nanoTime() - start) / 1000000) + "ms");
// Using String.format
rdm = new Random(0);
start = System.nanoTime();
for(int i = 10000000; i != 0; i--){
String.format("%04d", rdm.nextInt(20000) - 10000);
}
System.out.println("String.format: " + ((System.nanoTime() - start) / 1000000) + "ms");
}
Result
结果
Own function:1697ms
自带函数：1697ms
String.format:38134ms
字符串格式：38134ms
回答by Fathah Rehman P
Check my code that will work for integer and String.
检查适用于整数和字符串的代码。
Assume our first number is 2. And we want to add zeros to that so the the length of final string will be 4. For that you can use following code
假设我们的第一个数字是 2。我们想给它加零，所以最终字符串的长度将为 4。为此，您可以使用以下代码
int number=2;
int requiredLengthAfterPadding=4;
String resultString=Integer.toString(number);
int inputStringLengh=resultString.length();
int diff=requiredLengthAfterPadding-inputStringLengh;
if(inputStringLengh<requiredLengthAfterPadding)
{
resultString=new String(new char[diff]).replace("<dependency>
<artifactId>guava</artifactId>
<groupId>com.google.guava</groupId>
<version>14.0.1</version>
</dependency>
", "0")+number;
}
System.out.println(resultString);
回答by Tho
You can use Google Guava:
您可以使用谷歌番石榴：
Maven:
马文：
String paddedString1 = Strings.padStart("7", 3, '0'); //"007"
String paddedString2 = Strings.padStart("2020", 3, '0'); //"2020"
Sample code:
示例代码：
int a = 11;
String with3digits = String.format("%03d", a);
System.out.println(with3digits);
Note:
笔记：
Guavais very useful library, it also provides lots of features which related to Collections, Caches, Functional idioms, Concurrency, Strings, Primitives, Ranges, IO, Hashing, EventBus, etc
Guava是非常有用的图书馆，还提供了很多这关系到功能Collections，Caches，Functional idioms，Concurrency，Strings，Primitives，Ranges，IO，Hashing，EventBus，等
Ref: GuavaExplained
参考：番石榴解释
回答by bvdb
Let's say you want to print 11as 011
假设您想打印11为011
You could use a formatter: "%03d".
您可以使用格式化程序："%03d"。
You can use this formatter like this:
您可以像这样使用此格式化程序：
System.out.printf("%03d", a);
Alternatively, some java methods directly support these formatters:
或者，一些 java 方法直接支持这些格式化程序：
##代码##