ماذا تتوقع من Java في 2020؟

مطابقة الأنماط على سبيل المثال (معاينة)

if (obj instanceof String) {
    String s = (String) obj;
    System.out.println(s.toUpperCase());
}

if (obj instanceof String s) {
   System.out.println(s.toUpperCase());
}

if (obj instanceof String) {
    String s = (String) obj;
    if (s.contains(“prefix_”)) {
       return s.toUpperCase();
    }
}
return null;

return (obj instanceof String s) && s.contains(“prefix_”) ? s.toUpperCase() : null;

مفيدة NullPointerExceptions

public String getStreetFromRequest(Request request) {
   return request.getAddress().getStreet().toUpperCase();
}

Exception in thread "main" java.lang.NullPointerException
	at Program.getStreetFromRequest(Program.java:10)
	at Program.main(Program.java:6)

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "String.toUpperCase()" because the return value of "Address.getStreet()" is null
	at Program.getStreetFromRequest(Program.java:10)
	at Program.main(Program.java:6)

السجلات (معاينة)

public class Request {
    private Address address;

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
       this.address = address;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Request request = (Request) o;
        return Objects.equals(address, request.address);
    }

    @Override
    public int hashCode() {
        return Objects.hash(address);
    }

    @Override
    public String toString() {
        return "Request{" +
                "address=" + address +
                '}';
    }
}

@Data
@AllArgsConstructor
public class Request {
    private Address address;
}

public record Request(Address address) {
}

public record Request(Address address) {
   private final String anotherParameter; // compilation error
}

كتل النص (المعاينة الثانية)

public static void main(String[] args) {
        final var test = """
                This is the long text block with escape string \s
                that is really well done            \s
                """;
        System.out.println(test);
}

public static void main(String[] args) {
        final var test = """
                This is the long text block with escape string \
                that is really well-done functional            
                """;
System.out.println(test);

وبعض الأشياء الأكثر إثارة للاهتمام.

الإصدار التالي. الفرح والإحباط

// 
public abstract sealed class Base {
   public static class ChildA extends Base{}
   public static class ChildB extends Base{}
}

// 
public sealed interface BaseInterface permits ChildC, ChildD{
}

//  
public class ChildC implements BaseInterface {
}
//  
public class ChildD implements BaseInterface {
}

استنتاج