基础篇 _练习 小练习5~14

/*小练习5 完成class C的代码部分*/interface A {void show();}interface B {void add(int a,int b);}class C implements A,B{//写吧。}public class lianxi_5 {public static void main(String[] args){C c=new C();c.add(4, 2);c.show();//通过该函数打印以上两个数的和。}}

答案：

/*小练习5*/package com.test2;interface A {void show();}interface B {void add(int a,int b);}class C implements A,B{<span style="color:#ff0000;">//int c;int a,b;public void add(int a, int b){//c=a+b;this.a=a;this.b=b;}public void show() {System.out.println(a+b);}</span>}public class lianxi_5 {public static void main(String[] args){C c=new C();c.add(4, 2);c.show();//通过该函数打印以上两个数的和。}}

/*<span style="white-space:pre"></span>小练习6：写出运行结果:*/package com.test2;class Super{int i=0;Super(String s){i=1;}}public class lianxi_8 extends Super{lianxi_8(String s){super(s);i=2;}public static void main(String[] args){lianxi_8 xi=new lianxi_8("yes");System.out.println(xi.i);答案：2<pre name="code" class="java">/*写出运行结果：*/

/*小练习7：写出运行结果

*/public class lianxi_9 {static void func(){try {throw new Exception();//System.out.println("A");//此处编译失败，因为执行不到。} catch (Exception e) {System.out.println("B");}}public static void main(String[] args) {try {func();} catch (Exception e){System.out.println("C");}System.out.println("D");}}

}}

答案：

/* <span style="font-family: Arial, Helvetica, sans-serif;">小练习8： </span><span style="font-family: Arial, Helvetica, sans-serif;">补足代码</span>*/package com.test3;interface Test{void func();}public class lianxi_10 {public static void main(String[] args){//补足代码，匿名内部类}void show (Test t){t.func();}}

答案：

/* <span style="white-space:pre"></span><span style="font-family: Arial, Helvetica, sans-serif;">小练习8：</span><span style="font-family: Arial, Helvetica, sans-serif;">补足代码：</span>*/package com.test3;interface Test{void func();}public class lianxi_10 {public static void main(String[] args){//补足代码，匿名内部类<span style="color:#ff0000;">lianxi_10 lx=new lianxi_10();lx.show(new Test(){public void func(){System.out.println("func run");}});</span>}void show (Test t){t.func();}}

/*小练习9:写出程序运行结果。*/package com.test3;public class llianxi_11 {public static String output="";static void foo(int i){try {if(i==1)throw new Exception();output+="1";} catch (Exception e) {output+="2";return;}finally{output+="3";}output+="4";}public static void main(String[] args) {foo(0);System.out.println(output);//134foo(1);System.out.println(output);//13423}}

/*小练习10：建立一个接口图形，声明一个面积函数。圆形和矩形都实现这个接口，并得出两个图形的面积。注：体现面向对象的特征，对数值进行判断。用异常处理，不合法的数值要出现“这个数值是非法的”提示，不再进行运算。*/

class NoException extends RuntimeException{NoException(String msg){super(msg);}}interface A{void getArea();}class Rect implements A{private int width,length;Rect(int width,int length) throws NoException{if(width<=0||length<=0)throw new NoException("这个数值是非法的");this.width=width;this.length=length;}public void getArea(){System.out.println(width*length);}}class Circle implements A{private int radius;private static final double PI=3.14;Circle(int radius) throws NoException{if(radius<=0)throw new NoException("这个数值是非法的");this.radius=radius;}public void getArea(){System.out.println(radius*radius*PI);}}public class lianxi_12 {public static void main(String[] args) {Rect r = new Rect(3,-4);r.getArea();//Circle c=new Circle(-10);//c.getArea();System.out.println("over");}}

/*小练习11：补足compare函数内的代码，不许添加其他函数。*/package com.test4;class Circle{private static double pi=3.14;private  double radius;public Circle(double r){this.radius=r;}public static double compare(Circle[] cir){//程序代码//其实就是在求数组中的最大值。<span style="color:#ff0000;">int max=0;//数组角标for(int i=1;i<cir.length;i++){if(cir[i].radius>cir[max].radius){max=i;}}return cir[max].radius;</span>}}public class lianxi_13 {public static void main(String[] args){Circle cir[]=new Circle[3];//创建了一个类类型数组cir[0]=new Circle(1.0);cir[1]=new Circle(2.0);cir[2]=new Circle(4.0);System.out.println("最大半径值为："+Circle.compare(cir));}}

 练习12：在一个类中编写一个方法，这个方法搜索一个字符数组中是否存在某个字符，     如果存在，则返回这个字符在字符数组第一次出现的位置（序号从0开始计算）     如果不存在，返回-1.要搜索的字符数组和字符都以参数形式传递给该方法，     如果传入的数组为null，应抛出IllegalArgumentException异常。     在类的main方法中一各种可能出现的情况测试验证该方法编写得是否正确。     例如：字符不存在，字符存在，传入数组为null等。

答案：

class ZiFu{//char[] a;//char b;//ZiFu(char[] a,char b)//{//this.a=a;//this.b=b;//}public int getIndex(char[] arr,char key){if(arr==null)throw new IllegalArgumentException("数组为空");for(int i=0;i<arr.length;i++){if(arr[i]==key){return i;}}return -1;}}public class lianxi_14 {public static void main(String[] args) {char[] arr=new char[]{'0','r','2','b','1','2'};ZiFu z=new ZiFu();z.getIndex(null, 'a');}}

/*<span style="font-family: Arial, Helvetica, sans-serif;">练习13：</span><span style="font-family: Arial, Helvetica, sans-serif;">补足compare函数内的代码，不许添加其他函数。</span>

<span style="font-family:Arial, Helvetica, sans-serif;"><span style="white-space:pre"></span>结合</span><span style="font-family: Arial, Helvetica, sans-serif;">小练习11：补足compare函数。一起看，对应的。</span><span style="font-family:Arial, Helvetica, sans-serif;"></span>*/package com.test5;class Circle{private double radius;Circle(double radius){this.radius=radius;}public Circle Compare(Circle cir){//程序代码return (this.radius>cir.radius)?this:cir;}}public class lianxi_13_1 {public static void main(String[] args){Circle cir1=new Circle(1.0);Circle cir2=new Circle(2.0);Circle cir;cir=cir1.Compare(cir2);if(cir==cir1)System.out.println("圆1的半径比较大");elseSystem.out.println("圆2的半径比较大");}}