嵌套类-如何将外部类变量用于内部类

public class OuterClass {
    private int outerVariable = 10;
    
    public class InnerClass {
        private int innerVariable;
        
        public InnerClass(int outerVariable) {
            this.innerVariable = outerVariable;
        }
        
        public void printVariables() {
            System.out.println("Outer variable: " + outerVariable);
            System.out.println("Inner variable: " + innerVariable);
        }
    }
    
    public static void main(String[] args) {
        OuterClass outer = new OuterClass();
        OuterClass.InnerClass inner = outer.new InnerClass(20);
        inner.printVariables();
    }
}

public class OuterClass {
    private int outerVariable = 10;
    
    public class InnerClass {
        public void printVariable(int outerVariable) {
            System.out.println("Outer variable: " + outerVariable);
        }
    }
    
    public static void main(String[] args) {
        OuterClass outer = new OuterClass();
        OuterClass.InnerClass inner = outer.new InnerClass();
        inner.printVariable(outer.outerVariable);
    }
}

public class OuterClass {
    private int outerVariable = 10;
    
    public class InnerClass {
        public int getOuterVariable() {
            return OuterClass.this.outerVariable;
        }
    }
    
    public static void main(String[] args) {
        OuterClass outer = new OuterClass();
        OuterClass.InnerClass inner = outer.new InnerClass();
        System.out.println("Outer variable: " + inner.getOuterVariable());
    }
}