java-coding-guideline

Java Coding Guideline

CRITICAL: These rules apply to ALL Java code unless explicitly overridden by more specific skills.

Import Statements

Always use explicit imports without wildcards for better code clarity and maintainability.

✅ Do

import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.fail;

❌ Don't

import static org.assertj.core.api.Assertions.*;

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Vertical Spacing (Readability)

Use consistent vertical spacing inside classes to make diffs smaller and code easier to scan.

Rule

• Insert exactly one blank line between:
  • field blocks and the next field block (when grouped)
  • fields and the first constructor
  • constructors and methods
  • methods and the next method
• Also insert one blank line right after the opening { of a class (before the first field/initializer), unless the class is intentionally empty.

✅ Do

public final class SomeClass {

    @NonNull
    private final String fieldA;

    @NonNull
    private final String fieldB;

    public void someFunc() {
        // some action
    }

    public String getFieldA() {
        return fieldA;
    }
}

❌ Don't

public final class SomeClass {
    @NonNull
    private final String fieldA;
    @NonNull
    private final String fieldB;
    public void someFunc() {
        // some action
    }
    public String getFieldA() {
        return fieldA;
    }
}

Constructors

Use a single primary constructor and delegate auxiliary constructors using this().

✅ Do

public final class SomeClass {

    private final int field1;
    private final int field2;

    public SomeClass() {
        this(1, 2);
    }

    public SomeClass(int field1, int field2) {
         this.field1 = field1;
         this.field2 = field2;
    }
}

❌ Don't

public final class SomeClass {

    private final int field1;
    private final int field2;

    public SomeClass() {
        this.field1 = 1;
        this.field2 = 2;
    }

    public SomeClass(int field1, int field2) {
         this.field1 = field1;
         this.field2 = field2;
    }
}