Properties

加载defaults.properties文件

defaults.properties内容如下    lastname=Smith获取properties属性（defaults.properties文件和TestController文件置于同级目录）    try (InputStream bundledResource = TestController.class.getResourceAsStream("defaults.properties")) {        Properties defaults = new Properties();        defaults.load(bundledResource);        return defaults;    } catch (IOException e) {        throw new UncheckedIOException( "defaults.properties not properly packaged" + " with application", e);    }

写Properties到xml文件

Properties prop = new Properties();prop.setProperty("name", "Steve");prop.setProperty("color", "green");prop.setProperty("age", "23");File file = new File("C:\\Users\\26401\\Desktop\\defaults.properties");if (!file.exists()){    file.createNewFile();}prop.storeToXML(new FileOutputStream(file), "testing properties with xml");
    
    
     
      testing properties with xml
     
     
      green
     
     
      Steve
     
     
      23
     
    

读Properties从xml文件

Properties prop = new Properties();File file = new File("C:\\Users\\26401\\Desktop\\defaults.properties");if (file.exists()){    prop.loadFromXML(new FileInputStream(file));    for (String name : prop.stringPropertyNames()){        System.out.println(name + "=" + prop.getProperty(name));    }}else {    System.err.println("Error: No file found at: " + file);}

Lambda表达式

自定义

Lambda表达式只能用于函数式接口函数式接口只能包含一个抽象方法，可以有多个default和static方法，可以有多个重写对象的方法@FunctionalInterfaceinterface MyFunctionalInterface {    void fn();}MyFunctionalInterface mfi = () -> System.out.println("函数式接口");mfi.fn();等价于MyFunctionalInterface mfi = new MyFunctionalInterface() {    @Override    public void fn() {        System.out.println("函数式接口");    }};

内置

Predicate
    
      p = o -> o.isEmpty();            // 返回值类型必须是布尔值Function
     
       f = o -> o.isEmpty();    // 返回值类型可以自定义Consumer
      
        c = o -> System.out.println(o);   // 返回值类型为voidc.accept("没有返回值");
      
     
    

sort方法中使用Lambada

原始写法List
    
      list = new ArrayList<>();list.add(3);list.add(1);list.add(2);Collections.sort(list, new Comparator
     
      (){    public int compare(Integer b, Integer l){        return b.compareTo(l);    }}); // [1,2,3]Lambada写法Collections.sort(list, (b, l) -> b.compareTo(l));或者Collections.sort(list, Comparator.comparing(Integer::valueOf));
     
    

序列化

文件序列化

public class SerialClass implements Serializable {    private static final long serialVersionUID = 1L;}

Gson序列化

        
     
      com.google.code.gson
         
     
      gson
         
     
      2.8.5
     
    public class User {    private Integer id;    private String name;    public User(Integer id, String name) {        this.id = id;        this.name = name;    }    getter...    setter...}// 序列化成jsonUser user = new User(1, "小李");Gson gson = new Gson();String json = gson.toJson(user);// 反序列化User userCopy = gson.fromJson(json, User.class);

Jackson序列化

依赖    
            
     
      com.fasterxml.jackson.core
             
     
      jackson-databind
             
     
      2.9.6
         
    json字符串转对象    ObjectMapper objectMapper = new ObjectMapper();    User outputObject = objectMapper.readValue( "{\"id\":\"1\",\"name\":\"小叶\"}", User.class);    outputObject.getName();    @JsonIgnoreProperties(ignoreUnknown = true) // 忽视反序列化遇到的不认识的属性    public class User {        ...    }对象转字符串    User user = new User(1, "小李");    ObjectMapper objectMapper = new ObjectMapper();    String json = objectMapper.writeValueAsString(user);

Comparable和Comparator

Comparable对象排序

public class User implements Comparable
    
      {    private Integer id;    private String name;    public User(Integer id, String name) {        this.id = id;        this.name = name;    }    public void setId(Integer id) {        this.id = id;    }    public Integer getId() {        return id;    }    public void setName(String name) {        this.name = name;    }    public String getName() {        return name;    }    @Override    public boolean equals(Object o) {        if (! (o instanceof User)) return false;        User p = (User)o;        return id.equals(p.id) && name.equals(p.name);    }    @Override    public int hashCode() {        return Objects.hash(id, name);    }    @Override    public int compareTo(User other) {        int idCompare = id.compareTo(other.id);        if (idCompare != 0) {            return idCompare;        } else {            return id.compareTo(other.id);        }    }}List
     
       list = Arrays.asList(new User(2, "小李"), new User(3, "小李"), new User(1, "小李"));Collections.sort(list);
     
    

Comparator对象排序

List
    
      list = Arrays.asList(new User(2, "小李"), new User(3, "小张"), new User(1, "小王"));Collections.sort(list, new Comparator
     
      () {    @Override    public int compare(User u1, User u2) {        return u1.getId().compareTo(u2.getId());    }});Collections.sort(list,(u1, u2) -> {    return u1.getId().compareTo(u2.getId());});Collections.sort(list,Comparator.comparing(User::getId).thenComparing(User::getName));
     
    

结语

本文章是java成神的系列文章之一如果你想知道，但是本文没有的，请下方留言我会第一时间总结出来并发布填充到本文