1.
TestArea.java
----------------------------------------
interface AreaInterface
{
public abstract float area();
}
class Rectangle implements AreaInterface
{
private float x, y;
public Rectangle(float X, float Y)
{
x = X;
y = Y;
}
@Override
public float area() {
return x * y;
}
public String toString()
{
return String.format("长方形的长为%1$.2f，宽为%2$.2f，面积为%3$.2f", x, y, area()) ;
}
}
public class TestArea {
public static void main(String[] args) {
Rectangle rectangle = new Rectangle(10.0f, 20.0f);
System.out.println(rectangle.toString());
}
}
----------------------------------------------
2.
TestInner.java
----------------------
class Outer{
private String s = "I am Outer.";
class Inner{
private String s = "I am Inner.";
public void say()
{
System.out.println(Outer.this.s);
System.out.println(this.s);
}
}
}
class TestInner {
public static void main(String[] args) {
Outer outer = new Outer();
Outer.Inner inner = outer.new Inner();
inner.say();
}
}
-------------------------------
3.
ClassA.java
-------------------
package package1;
public class ClassA {
public void methodA(){
System.out.println("I am methodA() in ClassA.");
}
}
---------------
ClassB.java
--------------------
package package2;
public class ClassB {
public void methodB(){
package1.ClassA classA = new package1.ClassA();
classA.methodA();
System.out.println("I am methodB() in ClassB.");
}
public static void main(String[] args) {
ClassB classB = new ClassB();
classB.methodB();
}
}