在Java中,防止在实例方法返回后更改字段

public class MyClass {
    private final int myField;

    public MyClass(int myField) {
        this.myField = myField;
    }

    public int getMyField() {
        return myField;
    }
}

public class MyClass {
    private int myField;

    public MyClass(int myField) {
        this.myField = myField;
    }

    public int getMyField() {
        return myField;
    }
}

import java.util.Collections;
import java.util.List;

public class MyClass {
    private final List<String> myList;

    public MyClass(List<String> myList) {
        this.myList = Collections.unmodifiableList(myList);
    }

    public List<String> getMyList() {
        return myList;
    }
}

import java.util.Optional;

public class MyClass {
    private final Optional<String> myField;

    public MyClass(String myField) {
        this.myField = Optional.ofNullable(myField);
    }

    public Optional<String> getMyField() {
        return myField;
    }
}