Java學習第三十七天＜面向物件習題＞＜異常體系＞＜五大執行異常＞＜異常處理＞＜異常習題＞
阿新 • • 發佈：2022-04-05
面向物件習題
package chapter14;
public class Homework01 {
public static void main(String[] args) {
Car c = new Car();
Car c1 = new Car(100);
System.out.println(c);//9 red
System.out.println(c1);//100 red
}
}
class Car{
double price=10;
static String color="white";//靜態只執行一次
public Car() {
this.price=9;
this.color="red";
}
public Car(double price) {
this.price = price;
}
@Override
public String toString() {
return price +"\t"+color;
}
}
package chapter14;
//靜態屬性所有物件共享
public class Homework02 {
public static void main(String[] args) {
int num=Frock.getNextNum();
System.out.println(num);//100100
int num2=Frock.getNextNum();
System.out.println(num2);//100200
Frock []p=new Frock[3];
p[0]=new Frock();
p[1]=new Frock();
p[2]=new Frock();
for (int i = 0; i < p.length ; i++) {
System.out.println(p[i].getSerialNumber());//100300-100500
}
}
}
class Frock{
private static int currentNum=100000;
public static int getNextNum() {
currentNum+=100;
return currentNum;
}
private int serialNumber;
public int getSerialNumber() {
return serialNumber;
}
public Frock() {
serialNumber=getNextNum();
}
}
package chapter14;
public class Homework03 {
public static void main(String[] args) {
Animal cat = new Cat();
cat.shout();
Animal dog = new Dog();
dog.shout();
}
}
abstract class Animal{
abstract void shout();
}
class Cat extends Animal{
@Override
void shout() {
System.out.println("貓叫");
}
}
class Dog extends Animal{
@Override
void shout() {
System.out.println("狗叫");
}
}
package chapter14;
public class Homework04 {
public static void main(String[] args) {
new Cellphone().testWork(1,2);
Cellphone2 C = new Cellphone2();
C.testWork(new cal(){
@Override
public double work(double n1, double n2) {//動態繫結
return n1+n2;
}
},2,3);
C.testWork(new cal() {
@Override
public double work(double n1, double n2) {
return n1*n2;
}
},3,6);
}
}
interface calc{
void work(double n1,double n2);
}
class Cellphone{
void testWork(double n1,double n2){
calc c= new calc() {
@Override
public void work(double n1, double n2) {
System.out.println(n1+n2);
}
};
c.work(n1,n2);
}
}
interface cal{
double work(double n1,double n2);
}
class Cellphone2{
public void testWork(cal d,double n1,double n2){
double result=d.work(n1,n2);//動態繫結，執行型別是匿名內部類
System.out.println(result);
}
}
package chapter14;
public class Homework05 {
public static void main(String[] args) {
new A().f1();
}
}
class A{
private static String name="xx";
public void f1(){
class B{//區域性內部類，是在方法裡的
private final String name="yy";
void show(){
System.out.println(name);//就近原則
System.out.println(A.name);
}
}
B b = new B();//區域性內部類呼叫
b.show();
}
}
package chapter14;
public class Homework06 {
public static void main(String[] args) {
Person p = new Person("唐僧", new Horse());
p.common();
p.passRiver();
p.passFireHill();//擴充套件
}
}
interface Vehicles{
void work();
}
class Horse implements Vehicles{
@Override
public void work() {
System.out.print("用馬");
}
}
class Boat implements Vehicles{
@Override
public void work() {
System.out.print("用船");
}
}
class Plane implements Vehicles{
@Override
public void work() {
System.out.print("用飛機");
}
}
class fac{//獲得工具類（返回建立的物件）
//優化 餓漢式，保持同一批馬
private static Horse horse=new Horse();
public static Horse getHorse(){
return horse;
}
private fac(){}//私有化構造器，防止外部類建立物件
public static Boat getBoat(){//做成static方法比較方便
return new Boat();
}
public static Plane getPlane(){
return new Plane();
}
}
class Person{
private String name;
private Vehicles V;
public Person(String name, Vehicles vehicles) {
this.name = name;
V = vehicles;
}
public void passRiver(){//情況動作當方法
if (!(V instanceof Boat)){//不是船或者空的時候
V =fac.getBoat();//V的編譯型別Vehicles，向上轉型，執行型別Boat
V.work();
System.out.println("過河");
}
}
public void common(){
if (V==null){
V =fac.getHorse();
}
V.work();
System.out.println("趕路");
}
public void passFireHill(){
if (!(V instanceof Plane)){
V =fac.getPlane();
V.work();
System.out.println("過火焰山");
}
}
}
package chapter14;
public class Homework07 {
public static void main(String[] args) {
Cars cars = new Cars(44.5);
cars.getAir().flow();
}
}
class Cars{
private double temperature;
public Cars(double temperature) {
this.temperature = temperature;
}
class Air{
public void flow(){
if (temperature>40){
System.out.println("吹冷氣");
}else if (temperature<0){
System.out.println("吹暖氣");
}else {
System.out.println("關閉");
}
}
}
public Air getAir(){//內部類建立
return new Air();
}
}
package chapter14;
public class Homework08 {
public static void main(String[] args) {
Color c=Color.BLACK;
c.show();
switch (c){
case RED:
System.out.println("紅");
c.show();
break;
case BLUE:
System.out.println("藍");
c.show();
break;
case BLACK:
System.out.println("黑");
c.show();
break;
case GREEN:
System.out.println("綠");
c.show();
break;
case YELLOW:
System.out.println("黃");
c.show();
break;
}
}
}
interface y{
void show();
}
enum Color implements y{
RED(255,0,0),BLUE(0,0,255),BLACK(0,0,0),YELLOW(255,255,0),GREEN(0,255,0);
private int redValue;
private int greenValue;
private int blueValue;
Color(int redValue, int greenValue, int blueValue) {
this.redValue = redValue;
this.greenValue = greenValue;
this.blueValue = blueValue;
}
@Override
public void show() {
System.out.println(redValue+","+greenValue+","+blueValue);
}
}
異常體系
五大執行異常
package chapter15.五大執行異常;
//異常處理，加強程式健壯性 ArithmeticException
public class Arithmetic {
public static void main(String[] args) {
int num1=10;
int num2=0;
try {//若沒有try catch 預設throw給jvm報錯
int res=num1/num2;//選中以後 Ctrl+alt+t 用try catch包起來
} catch (Exception e) {//系統將異常封裝成Exception物件e，傳遞給catch
e.printStackTrace();
System.out.println("異常原因："+e.getMessage());//輸出異常資訊
}
System.out.println("程式繼續執行");
}
}
package chapter15.五大執行異常;
public class ArrayIndexOutOfBounds {
public static void main(String[] args) {
int []arr={1,2,4};
for (int i = 0; i < arr.length+1 ; i++) {
System.out.println(arr[i]);
}
}
}
package chapter15.五大執行異常;
public class ClassCast {
public static void main(String[] args) {
A b = new B();
B b2=(B)b;//向下轉型，強轉
C c2=(C)b;//B與C無任何關係
}
}
class A{}
class B extends A{}
class C extends A{}
package chapter15.五大執行異常;
public class NullPointer {
public static void main(String[] args) {
String name=null;
System.out.println(name.length());
}
}
package chapter15.五大執行異常;
public class NumberFormat {
public static void main(String[] args) {
String name="123";
String h="哈哈";
int num=Integer.parseInt(name);//String轉成int
System.out.println(name);
Integer.parseInt(h);
}
}
異常處理
package chapter15.異常處理;
public class TryCatch01 {
public static void main(String[] args) {
try {
String h="哈哈";
Integer.parseInt(h);//String轉成int
System.out.println("xxx");//異常後不執行
} catch (NumberFormatException e) {//可用多個異常分別捕獲，子類異常在前父類在後
System.out.println(e.getMessage());
} finally {//必執行，含有return優先替代返回
System.out.println("finally執行....");
}
System.out.println("程式繼續....");
}
}
package chapter15.異常處理;
public class TryCatch02 {
public static int method(){
int i=1;
try {
i++;//2
String[]names=new String[3];
if (names[1].equals("tom")){//空指標異常，後面不執行
System.out.println(names[1]);
}else {
names[3]="xxxx";
}
return 1;
} catch (ArrayIndexOutOfBoundsException e) {
return 2;
}catch (NullPointerException b){
return ++i;//3 儲存，最後返回
}finally {
++i;//4
System.out.println("i="+i);//優先輸出i=4
}
}
public static void main(String[] args) {
System.out.println(method());
}
}
package chapter15.異常處理;
import java.util.Scanner;
public class TryCatchExercise {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
do {
System.out.println("請輸入整數");
// int i=scanner.nextInt(); 在try裡 記憶體資料沒有被取出，會誤以為使用者輸入 陷入無限迴圈
String input=scanner.next();
try {
int i=Integer.parseInt(input);
System.out.println("i="+i);
break;
} catch (NumberFormatException e) {
System.out.println("輸入不是整數");
}
}while (true);
}
}
package chapter15.異常處理;
//throws 異常處理方式，在方法宣告處後跟異常型別
//可丟擲父類異常，多個異常，子類方法只能丟擲父類的子類或相同異常
//丟擲的編譯異常在呼叫者裡必須處理（try catch或繼續丟擲去） 執行異常在呼叫者裡不是必須處理
public class Custom {
public static void main(String[] args) {
int age=180;
if (!(age>=18&&age<=120)){
throw new AgeException("年齡需18-20之間");//手動生成異常物件關鍵字，在方法體中後跟異常物件，可通過構造器設定資訊
}
System.out.println("年齡正確");
}
}
//自定義異常，一般情況下繼承RuntimeException，即做成執行時異常，可使用預設處理機制（呼叫者不用再丟擲）
class AgeException extends RuntimeException{
public AgeException(String message) {//構造器
super(message);
}
}
package chapter15.異常處理;
public class ThrowExercise {
public static void main(String[] args) {
try {
ReturnExceptionDemo.methodA();
}catch (Exception e){
System.out.println(e.getMessage());//3
}
ReturnExceptionDemo.methodB();
}
}
class ReturnExceptionDemo{
static void methodA(){
try {
System.out.println("進入方法A");//1
throw new RuntimeException("製造異常");
}finally {
System.out.println("用A方法的finally");//2
}
}
static void methodB(){
try {
System.out.println("進入方法B");//4
return;
}finally {
System.out.println("呼叫B方法finally");//5
}
}
}
異常習題
package chapter15.章節作業;
public class Homework01 {
public static void main(String[] args) {
try {
if(args.length!=2){
throw new ArrayIndexOutOfBoundsException("引數個數不對");
}
int n1=Integer.parseInt(args[0]);
int n2=Integer.parseInt(args[1]);
double res=cal(n1,n2);
System.out.println(res);
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println(e.getMessage());
}catch (NumberFormatException e){
System.out.println("引數格式不正確");
}catch (ArithmeticException g){
System.out.println("分母不能為0");
}
}
public static double cal(int n1,int n2){
return n1/n2;
}
}
package chapter15.章節作業;
public class Homework02 {
public static void func() {
try {
throw new RuntimeException();
}finally {
System.out.println("B");//1
}
}
public static void main(String[] args){
try {
func();
System.out.println("A");//有異常不執行
}catch (Exception b){
System.out.println("C");//2
}
System.out.println("D");//3 異常處理完了，就執行
}
}
package chapter15.章節作業;
public class Homework03 {
public static void main(String[] args) {
try{
showExce();
System.out.println("A");//不執行
}catch (Exception e){
System.out.println("B");//1
}finally {
System.out.println("C");//2
}
System.out.println("D");//3
}
public static void showExce()throws Exception{
throw new Exception();
}
}