How to Quickly Integrate Java 17 into Your Project Without Breaking Existing Code

Java 17 is now released, and many developers want to try it without affecting existing project environments.

Project Quick Integration of Java 17

Before publishing, Amazon Corretto JDK 17 and Zulu JDK 17 were already available.

Download a Java 17 JDK (e.g., from the OpenJDK website) and extract it to the user’s C:\Users\n1\.jdks directory. IDEA automatically detects JDKs placed in the .jdks folder.

No need to reconfigure system Java environment variables; the version control is project‑level and won’t affect other projects.

Create a Maven (or plain/Gradle) project. You need to set two things before coding.

Language Level

Set the JDK language level to Java 17 in IDEA via Ctrl+Alt+Shift+S and change the Language Level to 17.

Bytecode Version

Also set the compiler bytecode version to 17 via Ctrl+Alt+S in the indicated location.

Record Class

After configuring the environment, try the useful syntactic sugar Record .

Strictly speaking, this is not a new Java 17 feature; it first appeared in Java 14 and became a standard feature in Java 16, but it remains important in the LTS version.

Traditional data‑class definition:

public class MyRecord {
    private final String username;
    private final Integer age;

    public MyRecord(String username, Integer age) {
        this.username = username;
        this.age = age;
    }

    public String username() { return username; }
    public Integer age() { return age; }
    @Override
    public boolean equals(Object o) { /* ... */ }
    @Override
    public int hashCode() { /* ... */ }
    @Override
    public String toString() { /* ... */ }
}

Using record simplifies it to:

public record MyRecord(String username, Integer age) { }

This greatly reduces boilerplate and can replace Lombok in many cases.

Record Is Immutable

Record

is designed for immutable data transfer; after initialization, its fields cannot be changed, there are no setter methods, and it is naturally thread‑safe.

Superclass of Record

All classes declared with the record keyword extend java.lang.Record, similar to enums.

public abstract class Record {
    protected Record() {}
    @Override public abstract boolean equals(Object obj);
    @Override public abstract int hashCode();
    @Override public abstract String toString();
}

Consequently, every record overrides equals, hashCode, and toString.

How to determine whether a class is a Record ?

Traditional method: Record.class.isAssignableFrom(MyRecord.class) JDK provides a new method: MyRecord.class.isRecord() The Class API also offers getRecordComponents() to retrieve record component information.

RecordComponent[] recordComponents = MyRecord.class.getRecordComponents();

Record Cannot Use extends

Since a record’s implicit superclass is java.lang.Record and Java does not support multiple inheritance, using extends results in a compilation error.

Cannot Define Extra Instance Fields

Record fields must be declared in the canonical constructor; adding extra instance variables is illegal:

public record MyRecord(String username, Integer age) {
    private String gender; // illegal
}

Static fields are allowed, however.

Define Methods Carefully

Methods can be added, but they must not break the record’s immutability. Defining setters is discouraged.

Also note that a record’s getter methods are not in the setXXXX format.

Using Annotations

Annotations on record components affect the generated getter methods. Example:

public record MyRecord(@Deprecated String username, Integer age) { }

Compiled result:

public record MyRecord(String username, Integer age) {
    public MyRecord(@Deprecated String username, Integer age) {
        this.username = username;
        this.age = age;
    }
    public String getUsername() { return this.username; }
    /** @deprecated */
    @Deprecated
    public String username() { return this.username; }
    public Integer age() { return this.age; }
}

The effective scope of an annotation depends on its @Target meta‑annotation.

Summary

This article demonstrated how to quickly integrate Java 17 into a project without impacting existing projects, and introduced the Record class, highlighting its immutability, boilerplate reduction, and usage considerations.