常用知识点

1、合并数组

int [] arry1 = {1,2,3,4,5};
int [] arry2 = {6,7,8,9,0};
int [] arry3 = new int[arry1.length+arry2.length];
System.arraycopy(arry1, 0, arry3, 0, arry1.length);
System.arraycopy(arry2, 0, arry3, arry1.length, arry2.length);
System.out.println(Arrays.toString(arry3));
------------------------------------------------------------------------------
[1, 2, 3, 4, 5, 6, 7, 8, 9, 0]

 2、对象序列化为json，json反序列化为对象

try {
			D d = new D();
			d.setA("a");
			ObjectMapper om = new ObjectMapper();
			ObjectWriter ow = om.writerWithView(d.getClass());
			System.out.println(ow.writeValueAsString(d));
			
			ObjectReader or = om.reader(D.class);
			D s = or.readValue(ow.writeValueAsString(d));
			
			System.out.println(s.getA());
		} catch (JsonProcessingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} 
----------------------------------------------------------------------------------
{"a":"a","t":{"name":"zhangSan"},"paramTest":"param"}
a

 3、json转换为map（bean转换为map键值对）

   try {
			D d = new D();
			d.setA("a");
			d.setT(new T("zhangSan"));
			d.setParamTest("param");
			ObjectMapper om = new ObjectMapper();
			ObjectWriter ow = om.writerWithView(d.getClass());
			String result = ow.writeValueAsString(d);

			System.out.println(result);
			
			JSONObject jasonObject = JSONObject.fromObject(result);
			HashMap<String, Object> data = new HashMap<String, Object>();
			Iterator it = jasonObject.keys();
			// 遍历jsonObject数据，添加到Map对象
			while (it.hasNext()) {
				String key = String.valueOf(it.next());
				Object value = jasonObject.get(key);
				data.put(key, value);
			}
			
			System.out.println(data.toString());

		} catch (JsonProcessingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
-------------------------------------------------------------------------------------
{"a":"a","t":{"name":"zhangSan"},"paramTest":"param"}
{t={"name":"zhangSan"}, a=a, paramTest=param}

 4、进制转换

System.out.println(Integer.toBinaryString(8));//十进制转二进制
System.out.println(Integer.toHexString(8));//十进制转十六进制
System.out.println(Integer.toOctalString(8));//十进制转八进制  	
System.out.println(Integer.valueOf("1000", 2));//二进制转十进制
--------------------------------------------------------------------------------------
1000
8
10
8

 5、list自定义排序

 List<CollectionTest> list = new ArrayList<CollectionTest>();
    	list.add(new CollectionTest(1,DateUtils.addHours(new Date(), 2)));
    	list.add(new CollectionTest(2,DateUtils.addHours(new Date(), 1)));
    	list.add(new CollectionTest(3,DateUtils.addHours(new Date(), 4)));
    	list.add(new CollectionTest(4,DateUtils.addHours(new Date(), 3)));
    	
        //这里是倒序
    	Collections.sort(list, new Comparator<CollectionTest>() {
			@Override
			public int compare(CollectionTest arg0, CollectionTest arg1) {
				if (arg0.getOrder1().getTime() < arg1.getOrder1().getTime()) {
					return 1;
				} else if (arg0.getOrder1().getTime() > arg1.getOrder1().getTime()) {
					return -1;
				} else {
					return 0;
				}
			}
		});
    	
    	for (CollectionTest collectionTest : list) {
			System.out.println(collectionTest.getOrder());
			System.out.println(collectionTest.getOrder1());
		}
-----------------------------------------------------------------------------------------
3
Fri Jun 26 21:19:05 CST 2015
4
Fri Jun 26 20:19:05 CST 2015
1
Fri Jun 26 19:19:05 CST 2015
2
Fri Jun 26 18:19:05 CST 2015 

6、正则表达式基本使用

Pattern p=Pattern.compile(".*.*/.*.*/service/.*.*/.*Service.*");
System.out.println(p.matcher("com/paic/cicp/test/biz/service/impl/UserServiceImpl").matches());
System.out.println(p.matcher("com/paic/cicp/test/biz/service/impl/UserService.i").matches());
String s = "123";
System.out.println(s.matches("\\d{3}"));
---------------------------------------------------------------------------------------
true
true
true

 7、分隔，代替split

StringTokenizer tokenizer = new StringTokenizer("I|身份证", "|");
System.out.println(tokenizer.nextToken());
System.out.println(tokenizer.nextToken());
----------------------------------------------------------------------------------------
I
身份证

 8、浅复制、深复制

//浅复制（只复制基本类型，不支持自定义复杂类型）
BeanUtils.cloneBean(object)；

//深复制（串行化，支持自定义复杂类型，要求自定义类型实现Serializable）
public static Object deepClone(Object src) throws Throwable {   
        ByteArrayOutputStream baos = new ByteArrayOutputStream();   
        ObjectOutputStream oos = new ObjectOutputStream(baos);   
        oos.writeObject(src);   
        oos.close();   
  
        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());   
        ObjectInputStream ois = new ObjectInputStream(bais);   
  
        Object o = ois.readObject();   
        ois.close();   
        return o;   
    }

//深复制（通过序列换、反序列化实现，支持自定义复杂类型，要求自定义类型实现Serializable）
public static <T> T deepClone1(T t){
    	
    	T r = null;
    	try {
    		ObjectMapper om = new ObjectMapper();
        	ObjectWriter ow = om.writerWithView(t.getClass());
        	String serResult = ow.writeValueAsString(t);
        	System.out.println(serResult);

        	ObjectReader or = om.reader(t.getClass());
			r = or.readValue(serResult);
		} catch (JsonProcessingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
    	
    	return r;
    }    	

 9、判断字符串是否数字（整数、小数、负数）

public static boolean isNum(String str){
		if(StringUtils.isBlank(str))
			return false;
		else if(str.matches("^\\d+$|-\\d+$") || str.matches("\\d+\\.\\d+$|-\\d+\\.\\d+$")) 
			return true;
		return false;
	}

 

 10、

 

 11、

 

 12、

 

 13、

 

 14、

 

 15、

 

 16、

 

 17、

 

 18、

 

 19、

 

 20、