Jakarta Commons Cookbook notes(一)-优快云博客

本文链接：https://blog.youkuaiyun.com/sunxboy/article/details/83798720

本文详细介绍了Java实用工具包commons-lang的功能，包括字符串操作、数组处理、日期格式化等常见任务的方法实现。此外还展示了如何利用该工具包进行数组转换、查找元素、日期处理等实用操作。

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jar name: commons-lang

一.　Supplements to the java 2 platform

1. toString()

public void toString() {
  ReflectionToStringBuilder.toString(this);
}

2. hashCode()

public int hashCode() {
 return HashCodeBuilder.reflectionHashCode(this);
}

3. equal()

public boolean equals(Object o){
 return EqualBuilder.reflectionEquals(this,o);
}

4. compareTo()

public int compareTo(Object o) {
  return CompareToBuilder.reflectionCompare(this,o);
}

5. print a array

int[] intArray = new int[] {2,3,4,5,6}
ArrayUtils.toString(intArray));

6. cloning and reversing arrays

long array[] array = {1,3,2,3,5,6};
long[] reversed = ArrayUtils.clone(array);
ArraysUtils.reverse(reversed);

7. transforming between object arrays and primitive array

long primitiveArray = new long[] {12,100,2929,3223};
Long[] objectArray = ArrayUtils.toObject(primitiveArray);

// null values in the object array are stored as Double.NaN
ArrayUtils.toPrivimitive(doubleObject,Double.NaN);

8. find items in an array

String[] stringArray = {"red","orange","blue","brown","red"};
boolean containsBlue = ArraysUtils.contains(stringArray,"blue");
int indexOfRed = ArraysUtils.indexOf(stringArray,"red");
int lastIndexOfRed = ArraysUtils.lastIndexOf(stringArray,"red");

9. creating a map from multidimensional array

Object[] weightArray = new Object[][] {{"H", new Double(1.0003)},
							     {"He", new Double(4.0002)},
                               {"Li", new Double(6.032)});
Map weights = ArraysUtils.toMap(weightArray);

10. formatting dates

// thead-safe formatter for java
DateFormatUtils.ISO_DATETIME_TIME_ZONE_FORMAT.format(new Date());

11. Rounding date objects

DateUtils.round(new Date(), Calendar.HOUR);
DateUtils.round(new Date(), Calendar.DATE_OF_MONTH);
DateUtils.round(new Date(), Calendar.YEAR);

12. truncating date object

DateUtils.truncat(new Date(), Calendar.MONTH);
DateUtils.truncat(new Date(), Calendar.HOUR);

13. Generating unique numberic identifiers

LonIdentifierFactory idfactory = IdentifierUtils.LongGenerator(false,0);
idFactory.nextLongIdentifier();

14. measure time

StopWatch clock = new StopWatch();
clock.start();
clock.stop();
clock.getTime();
clock.reset();