Java Coding Tips

你的名字 2022-05-27 02:54 132阅读 0赞

## Print Map in Java ##

> Arrays.toString(map.entrySet().toArray())

## Print List in Java ##

> Arrays.toString(list.toArray())

## 拼接List的字符串 ##

> String.join(‘delimiter’, ListObject)

List<String> list = Arrays.asList("one", "two", "three");
    System.out.println("Joined String:" + String.join(",", list));

输出结果为：

System.out.println("Joined String:" + String.join(",", list));

## List的数据操作 ##

> list.replaceAll(s-> s.toUpperCase())

List<String> list = Arrays.asList("one", "two", "three");
    System.out.println("before modification: " + list);
    list.replaceAll(s -> s.toUpperCase());
    System.out.println("after modification: " + list);

输出结果为：

before modification: [one, two, three]
    after modification: [ONE, TWO, THREE]

## 模式匹配 ##

@Test
    public void isPositiveInteger() {
    	System.out.println("\n*** Positive Intger *****");
    	String pattern = "^\\+?[1-9]\\d*"; //? -- {0,1}
    		
    	System.out.println("90:" + "90".matches(pattern));
    	System.out.println("9:" + "9".matches(pattern));
    	System.out.println("90.1:" + "90.1".matches(pattern));
    	System.out.println("-9:" + "-9".matches(pattern));
    	System.out.println("00:" + "00".matches(pattern));
    }
    
    @Test
    public void isNegativeInteger() {
    	System.out.println("\n*** Negative Intger *****");
        String pattern = "^-[1-9]\\d*";
    		
    	System.out.println("90:" + "90".matches(pattern));
    	System.out.println("90.1:" + "90.1".matches(pattern));
    	System.out.println("-9:" + "-9".matches(pattern));
    	System.out.println("00:" + "00".matches(pattern));
    	System.out.println("-0.1:" + "00".matches(pattern));
    }
    	
    @Test
    public void isWholeNumber() {
    	System.out.println("\n ***  is Pure Number ****");
    	String numberPattern = "[+-]?0";
    		
    	System.out.println("+0:" + "+0".matches(numberPattern));
    	System.out.println("-0:" + "-0".matches(numberPattern));
    	System.out.println("0:" + "0".matches(numberPattern));
    		
    	//combine three pattern 0, isNegative, isPositive
    }
    	
    @Test
    public void isNegativeDecimal() {
    	System.out.println("\n ***  is Negative Number ****");
    	String decimalPattern = "^-[0]\\.[1-9]*|^-[1-9]\\d*\\.\\d*";
    		
    	System.out.println("-12.1:" + "-12.1".matches(decimalPattern));
    	System.out.println("-122:" + "-122".matches(decimalPattern));;
    	System.out.println("122:" + "122".matches(decimalPattern));;
    	System.out.println("0.2:" + "0.2".matches(decimalPattern));;
    }
    	
    @Test
    public void isPositveDecimal() {
    	System.out.println("\n ***  is Positive Number ****");
    	String positvePattern = "\\+{0,1}[0]\\.[1-9]*|\\+{0,1}[1-9]\\d*\\.\\d*";
    		
    	System.out.println("-12.1:" + "-12.1".matches(positvePattern));
    	System.out.println("-122:" + "-122".matches(positvePattern));;
    	System.out.println("122:" + "122".matches(positvePattern));;
    	System.out.println("0.2:" + "0.2".matches(positvePattern));;
    }

### Map To List ###

> map.values().stream().collect(Collectors.toList());

List to Map:

> Map<String, BigDecimal> result = listDevs.stream().collect(Collectors.toMap(Developer :: getName, Developer :: getSal));

## Java Project Maven Profile Variable ##

*  $\{project.activeProfiles\[0\].id\} ： 当前活跃的profile的id
 *  $\{project.profiles\[0\].id\} ： 当前的profile的第一个的id

## 构建Request URL ##

String url = "http://localhost:8080/demo";
     UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl(url)
                    .queryParam("msisdn", "msisdn")
                    .queryParam("email", "email")
                    .queryParam("clientVersion", "clientVersion")
                    .queryParam("clientType", "clientType")
                    .queryParam("issuerName", "issuerName")
                    .queryParam("applicationName", "applicationName");
      log.info("uri:{}", builder.toUriString());

## Object Operation ##

BeanUtils.copyProperties(Object source, Object target, Class editable, String\[\] ignoreProperties)  
apache common BeanUtils.copyProperties()  
org.apache.commons.beanutils.PropertyUtils.copyProperties(Object dest, Object orig)