JAVA菜鸟入门(13) outer class与inner class的之间能互相使用field或者method吗?

Nested classes are divided into two categories: static and non-static. 

1. Nested classes that are declared static are called static nested classes. 

2. Non-static nested classes are called inner classes.

outer class与inner class的之间能互相使用field或者method吗?

可以。

代码如下:

package FFtest2;

public class FFOuter {
private String first;
private int second;
public FFOuter(String l, int r) {
first = l;
second = r;
}

public String addStringInteger(String first, int second) {
return first + Integer.toString(second);
}

/**
* test1
* Outter class has access to inner private field
* Outter class has access to inner method
*/
public void outterPrint() {
FFOuter.InnerDisplay temp = this.new InnerDisplay("frog", 20);
System.out.println("Outer class uses Inner class field : " + temp.innerFirst + ", " + temp.innerSecond);
temp.print(first, second);
}

private class InnerDisplay {
private String innerFirst;
private int innerSecond;
public InnerDisplay() {
this("Somebody", 0);
}
public InnerDisplay(String s, int i) {
innerFirst = s;
innerSecond = i;
}
public void print (String f, int s) {
System.out.println("Inner class: first = " + f+  ", second = " + s);
}

/**
* test 2
* Inner class has access to outer class private field
*/
public void print () {
System.out.println("Inner class uses outer class: first = " + first+  ", second = " + second);
}

/**
* test 3
* Inner class has access to outer class method.
*/
public String add(String first, int second)
{
return addStringInteger(first, second);
}
}

public static void main (String [] args){

/**
* test 4
* in main(), call outter method
* */
FFOuter outter = new FFOuter("zebra", 25);
outter.outterPrint();

/**
* test 5
* in main(), call inner method
*/
InnerDisplay innerDisplay = outter.new InnerDisplay();
innerDisplay.print();
System.out.println(innerDisplay.add("iphone", 10));
}
}

输出结果

Outer class uses Inner class field : frog, 20
Inner class: first = zebra, second = 25
Inner class uses outer class: first = zebra, second = 25
iphone10