Other Standards - Java

1. No Business Logic in Constructors

Put initialization logic in an init() method and call it from the constructor:

// Correct
public class Fish {
    public Fish() {
        init();
    }
    public void init() {
        // initialization logic
    }
}

// Wrong
public class Fish {
    public Fish() {
        // business logic written directly here
    }
}

2. Do Not Pass null to Constructors or Public Methods

null arguments are hard to understand from a method signature alone. Provide overloaded methods instead:

// Utility method
public class Utils {
    public static Border createBorder(Font font, Color color) {
        if (color == null) {
            color = new Color(223, 122, 123);
        }
        // ...
    }
}

// Correct: add an overload
public static Border createBorder(Font font) {
    return createBorder(font, null);
}
Border border = Utils.createBorder(font);

// Wrong
Border border = Utils.createBorder(font, null);

3. Internationalize All User-Visible Text

// Wrong
String shapeName = "Circle";

// Correct
String shapeName = Inter.getLocText("FR-Designer_Chart_Circle");

4. Never Return null from Array-Returning Methods — Use an Empty Array

// Correct
public String[] getNames() {
    if (a) {
        return new String[]{"Alice", "Bob"};
    } else {
        return new String[0];
    }
}

// Wrong
public String[] getNames() {
    if (a) {
        return new String[]{"Alice", "Bob"};
    } else {
        return null;  // callers risk a NullPointerException
    }
}

5. Every switch case Must Have a Corresponding break or return

Prevent fall-through from causing logic errors:

// Correct
switch (type) {
    case 1:
        someDescription = "qwe";
        break;
    case 2:
        someDescription = "xyz";
        break;
    default:
        someDescription = "mnx";
        break;
}

// Wrong (case 1 falls through into case 2)
switch (type) {
    case 1:
        someDescription = "qwe";
    case 2:
        someDescription = "xyz";
        break;
    ...
}

6. hashCode and equals Rules

If you override equals, you must also override hashCode.
Objects stored in a Set must override both methods.
Custom objects used as Map keys must override both hashCode and equals.

7. Use toArray(T[] array) When Converting a Collection to an Array

List<String> list = new ArrayList<>(2);
list.add("guan");
list.add("bao");

// Correct
String[] array = list.toArray(new String[0]);

// Wrong
Object[] array = list.toArray();

8. Do Not add or remove Elements Inside a foreach Loop

Use an Iterator instead. In concurrent scenarios, synchronize on the Iterator.

9. Simplify Boolean Returns

// Wrong
if (booleanExpression) {
    return true;
} else {
    return false;
}

// Correct
return booleanExpression;

10. Apply Strict Access Control to Class Members

protected fields are prohibited (they cannot be handled compatibly in the future).
Methods and variables used only within the current class must be declared private.

11. Always Add @Override When Overriding a Method

This catches incompatibilities when a parent class method signature changes:

// Correct
@Override
public void doSomething() {
    // custom implementation
}

During plugin development, FanRuan framework upgrades may change interface signatures. @Override ensures such breaking changes are caught at compile time.

Other Standards