Apache Commons包的工具類

 

Lang(http://commons.apache.org/proper/commons-lang/)

版本：commons-lang3-3.1.jar 

org.apache.commons.lang中的StringUtils類操做對象是java.lang.String類型的對象,是JDK提供的String類型操做方法的補充,而且是null安全的(即若是輸入參數String爲null則不會拋出NullPointerException，而是作了相應處理，例如，若是輸入爲null則返回也是null等.

這個工具包能夠當作是對java.lang的擴展。提供了諸如StringUtils, StringEscapeUtils, RandomStringUtils, Tokenizer, WordUtils等工具類。

Class Summary

Class	Description
ArrayUtils	Operations on arrays, primitive arrays (like int[]) and primitive wrapper arrays (like Integer[]).
CharEncoding	Character encoding names required of every implementation of the Java platform.
ClassPathUtils	Operations regarding the classpath.
ClassUtils	Operates on classes without using reflection.
RandomStringUtils	Operations for random Strings.
RandomUtils	Utility library that supplements the standard Random class.
StringUtils	Operations on String that are null safe.
SystemUtils	Helpers for java.lang.System.
ThreadUtils	Helpers for java.lang.Thread and java.lang.ThreadGroup.
Validate	This class assists in validating arguments.

示例:

其中對幾個現階段用的比較多的包中類的經常使用方法作介紹,不按期更新

• 字符串爲空判斷

//isEmpty
//Checks if a CharSequence is empty ("") or null.

System.out.println(StringUtils.isEmpty(null));      // true
System.out.println(StringUtils.isEmpty(""));        // true
System.out.println(StringUtils.isEmpty(" "));       // false
System.out.println(StringUtils.isEmpty("bob"));     // false
System.out.println(StringUtils.isEmpty("  bob  ")); // false

//isBlank
//Checks if a CharSequence is whitespace, empty ("") or null.
System.out.println(StringUtils.isBlank(null));      // true
System.out.println(StringUtils.isBlank(""));        // true
System.out.println(StringUtils.isBlank(" "));       // true
System.out.println(StringUtils.isBlank("bob"));     // false
System.out.println(StringUtils.isBlank("  bob  ")); // false

 

• 字符串的Trim

//trim 去掉首尾的空格
System.out.println(StringUtils.trim(null)); // null
System.out.println(StringUtils.trim("")); // ""
System.out.println(StringUtils.trim("     ")); // ""
System.out.println(StringUtils.trim("abc")); // "abc"
System.out.println(StringUtils.trim("    abc")); // "abc"
System.out.println(StringUtils.trim("    abc  ")); // "abc"
System.out.println(StringUtils.trim("    ab c  ")); // "ab c"

//strip
System.out.println(StringUtils.strip(null)); // null
System.out.println(StringUtils.strip("")); // ""
System.out.println(StringUtils.strip("   ")); // ""
System.out.println(StringUtils.strip("abc")); // "abc"
System.out.println(StringUtils.strip("  abc")); // "abc"
System.out.println(StringUtils.strip("abc  ")); // "abc"
System.out.println(StringUtils.strip(" abc ")); // "abc"
System.out.println(StringUtils.strip(" ab c ")); // "ab c"

• 字符串的分割

//默認半角空格分割
String str1 = "aaa bbb ccc";
String[] dim1 = StringUtils.split(str1); // => ["aaa", "bbb", "ccc"]

System.out.println(dim1.length);//3
System.out.println(dim1[0]);//"aaa"
System.out.println(dim1[1]);//"bbb"
System.out.println(dim1[2]);//"ccc"

//指定分隔符
String str2 = "aaa,bbb,ccc";
String[] dim2 = StringUtils.split(str2, ","); // => ["aaa", "bbb", "ccc"]

System.out.println(dim2.length);//3
System.out.println(dim2[0]);//"aaa"
System.out.println(dim2[1]);//"bbb"
System.out.println(dim2[2]);//"ccc"

//去除空字符串
String str3 = "aaa,,bbb";
String[] dim3 = StringUtils.split(str3, ","); // => ["aaa", "bbb"]

System.out.println(dim3.length);//2
System.out.println(dim3[0]);//"aaa"
System.out.println(dim3[1]);//"bbb"

//包含空字符串
String str4 = "aaa,,bbb";
String[] dim4 = StringUtils.splitPreserveAllTokens(str4, ","); // => ["aaa", "", "bbb"]

System.out.println(dim4.length);//3
System.out.println(dim4[0]);//"aaa"
System.out.println(dim4[1]);//""
System.out.println(dim4[2]);//"bbb"

//指定分割的最大次數（超事後不分割）
String str5 = "aaa,bbb,ccc";
String[] dim5 = StringUtils.split(str5, ",", 2); // => ["aaa", "bbb,ccc"]

System.out.println(dim5.length);//2
System.out.println(dim5[0]);//"aaa"
System.out.println(dim5[1]);//"bbb,ccc"

 

• 字符串的鏈接

  //數組元素拼接
  String[] array = {"aaa", "bbb", "ccc"};
  String result1 = StringUtils.join(array, ","); 
  
  System.out.println(result1);//"aaa,bbb,ccc"
  
  //集合元素拼接
  List<String> list = new ArrayList<String>();
  list.add("aaa");
  list.add("bbb");
  list.add("ccc");
  String result2 = StringUtils.join(list, ",");
  
  System.out.println(result2);//"aaa,bbb,ccc"

  •  

對於StingUtils的字符串處理類經常使用方法就這些,還有些方法根據具體代碼需求查閱Api文檔

對於ArrayUtils類,經常使用方法以下:

// 追加元素到數組尾部
int[] array1 = {1, 2};
array1 = ArrayUtils.add(array1, 3); // => [1, 2, 3]

System.out.println(array1.length);//3
System.out.println(array1[2]);//3

// 刪除指定位置的元素
int[] array2 = {1, 2, 3};
array2 = ArrayUtils.remove(array2, 2); // => [1, 2]

System.out.println(array2.length);//2

// 截取部分元素
int[] array3 = {1, 2, 3, 4};
array3 = ArrayUtils.subarray(array3, 1, 3); // => [2, 3]

System.out.println(array3.length);//2

// 數組拷貝
String[] array4 = {"aaa", "bbb", "ccc"};
String[] copied = (String[]) ArrayUtils.clone(array4); // => {"aaa", "bbb", "ccc"}
		
System.out.println(copied.length);//3		

// 判斷是否包含某元素
String[] array5 = {"aaa", "bbb", "ccc", "bbb"};
boolean result1 = ArrayUtils.contains(array5, "bbb"); // => true		
System.out.println(result1);//true

// 判斷某元素在數組中出現的位置（從前日後，沒有返回-1）
int result2 = ArrayUtils.indexOf(array5, "bbb"); // => 1		
System.out.println(result2);//1

// 判斷某元素在數組中出現的位置（從後往前，沒有返回-1）
int result3 = ArrayUtils.lastIndexOf(array5, "bbb"); // => 3
System.out.println(result3);//3

// 數組轉Map
Map<Object, Object> map = ArrayUtils.toMap(new String[][]{
	{"key1", "value1"},
	{"key2", "value2"}
});
System.out.println(map.get("key1"));//"value1"
System.out.println(map.get("key2"));//"value2"

// 判斷數組是否爲空
Object[] array61 = new Object[0];
Object[] array62 = null;
Object[] array63 = new Object[]{"aaa"};

System.out.println(ArrayUtils.isEmpty(array61));//true
System.out.println(ArrayUtils.isEmpty(array62));//true
System.out.println(ArrayUtils.isNotEmpty(array63));//true

// 判斷數組長度是否相等
Object[] array71 = new Object[]{"aa", "bb", "cc"};
Object[] array72 = new Object[]{"dd", "ee", "ff"};

System.out.println(ArrayUtils.isSameLength(array71, array72));//true

// 判斷數組元素內容是否相等
Object[] array81 = new Object[]{"aa", "bb", "cc"};
Object[] array82 = new Object[]{"aa", "bb", "cc"};

System.out.println(ArrayUtils.isEquals(array81, array82));

// Integer[] 轉化爲 int[]
Integer[] array9 = new Integer[]{1, 2};
int[] result = ArrayUtils.toPrimitive(array9);

System.out.println(result.length);//2
System.out.println(result[0]);//1

// int[] 轉化爲 Integer[] 
int[] array10 = new int[]{1, 2};
Integer[] result10 = ArrayUtils.toObject(array10);

System.out.println(result.length);//2
System.out.println(result10[0].intValue());//1

BeanUtils(http://commons.apache.org/proper/commons-beanutils/)

經常使用屬性整理以下:

Method Summary

Methods 

Modifier and Type	Method and Description
static Object	cloneBean(Object bean) Clone a bean based on the available property getters and setters, even if the bean class itself does not implement Cloneable. (基於可用的屬性getter和setter來克隆一個bean，即便bean類自己沒有實現Cloneable。)
static void	copyProperties(Object dest, Object orig) Copy property values from the origin bean to the destination bean for all cases where the property names are the same. 對於屬性名稱相同的全部狀況，將屬性值從origin bean複製到目標bean。
static void	copyProperty(Object bean, String name, Object value) Copy the specified property value to the specified destination bean, performing any type conversion that is required. 將指定的屬性值複製到指定的目標bean，執行所需的任何類型轉換。
static Map<String,String>	describe(Object bean) Return the entire set of properties for which the specified bean provides a read method. (返回指定的bean提供讀取方法的整個屬性集)
static String[]	getArrayProperty(Object bean, String name) Return the value of the specified array property of the specified bean, as a String array. 將指定的bean的指定數組屬性的值做爲String數組返回。
static String	getIndexedProperty(Object bean, String name) Return the value of the specified indexed property of the specified bean, as a String. 將指定的bean的指定索引屬性的值做爲String返回。
static String	getIndexedProperty(Object bean, String name, int index) Return the value of the specified indexed property of the specified bean, as a String. 將指定的bean的指定索引屬性的值做爲String返回。
static String	getMappedProperty(Object bean, String name) Return the value of the specified indexed property of the specified bean, as a String.
static String	getMappedProperty(Object bean, String name, String key) Return the value of the specified mapped property of the specified bean, as a String. 返回指定bean的指定映射屬性的值，做爲字符串。
static String	getNestedProperty(Object bean, String name) Return the value of the (possibly nested) property of the specified name, for the specified bean, as a String. 將指定的bean的（可能嵌套的）屬性的值做爲String返回。
static String	getProperty(Object bean, String name) Return the value of the specified property of the specified bean, no matter which property reference format is used, as a String.
static String	getSimpleProperty(Object bean, String name) Return the value of the specified simple property of the specified bean, converted to a String.
static void	populate(Object bean, Map<String,? extends Object> properties) Populate the JavaBeans properties of the specified bean, based on the specified name/value pairs. 根據指定的名稱/值對，填充指定的bean的JavaBeans屬性
static void	setProperty(Object bean, String name, Object value) Set the specified property value, performing type conversions as required to conform to the type of the destination propert     設置指定的屬性值，根據須要執行類型轉換以符合目標屬性的類型

示例:

複製Bean  //public static Object cloneBean(Object bean)

Book bk=new Book();
            bk.setTitle("java編程");
            bk.setContent("java編程語言");  
           //public static Object cloneBean(Object bean)
            Book copyBean=(Book)BeanUtils.cloneBean(bk);
            System.out.println(copyBean.getTitle());
            System.out.println(copyBean.getContent());

 賦值Bean  //public static void copyProperties(Object dest,Object orig)

JavaBook javabook=new JavaBook();
         javabook.setTitle("JAVA類書籍");
         javabook.setContent("java併發編程");
         javabook.setZhuozhe("不祥");
         Book bk=new Book();
       //copyProperties(Object dest, Object orig)
        BeanUtils.copyProperties(bk, javabook);
        System.out.println(bk.getTitle());
        System.out.println(bk.getContent());

   // copyProperty(Object bean, String name, Object value)
        BeanUtils.copyProperty(javabook, "title", "測試書籍");
  //public static String getProperty(Object bean, String name)
   System.out.println(BeanUtils.getProperty(bk, "title"));

Bean的populate // populate(Object bean, Map<String,? extends Object> properties)

Book bk=new Book();
        Map<String, String> map5 = new HashMap<String, String>();  
        map5.put("title", "rensanning");  
        map5.put("content", "31");  
//        public static void populate(Object bean, Map<String,? extends Object> properties)
       BeanUtils.populate(bk, map5);
       System.out.println(BeanUtils.getProperty(bk, "title"));
       System.out.println(BeanUtils.getProperty(bk, "content"));

其餘方法根據實際應用參照API

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                                                                                      2017年4月7日18:23:15