Java 语言程序设计实践环节（04748）是 Java 语言程序设计（一）专业课的上级测试部分，考核目标是掌握调试、完善和简单设计 Java 程序的能力、掌握 MyEclipse 开发工具的使用（新建项目，新建类，修改与运行程序）、掌握 Java 的基本语句，基本输入输出流、掌握使用类及方法进行 Java 面向对象程序开发的方法。运行环境是 Windows 10 系统下的 MyEclipse 软件。以下为我在学习和实战练习过程中所做的笔记，可供参考。
一、输入、输出语句
使用 Scanner 语句输入时需要引入包 import java.util.Scanner; ，并定义 Scanner 对象：
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| import java.util.Scanner;
public class Test1 {
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
String temp = sc.next();
System.out.println("temp："+ n);
}
}
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BufferedReader 由 Reader 类扩展而来，提供通用的缓冲方式文本读取，而且提供了很实用的 readLine，读取一个文本行，从字符输入流中读取文本，缓冲各个字符，从而提供字符、数组和行的高效读取。使用 BufferedReader 流前需要引入 import java.io.Reader;：
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| import java.io.*
public class Test2 {
public static void main(String[] args){
String st;
int num;
float fnum;
try{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
st = br.readLine();
num = Integer.parseInt(br.readLine());
fnum = Float.parseFloat(br.readLine());
System.out.println(st + num + snum);
}catch(IOException e){
System.out.println("错误");
}
}
}
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二、实现常见的基本算法
字符统计程序。编写输入字符行，统计输入字符行中数字符、英文字母个数的 Java 应用程序：
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| import java.util.Scanner;
public class Test3 {
public static void main(String[] args) {
int a = 0 ;
int b = 0 ;
int c = 0 ;
int d = 0 ;
Scanner sc = new Scanner(System.in) ;
System.out.println("请输入一串字符串");
String s = sc.nextLine() ;
char[] sr = s.toCharArray() ;
for(int i = 0 ;i<sr.length ; i ++ ) {
if('A'<=sr[i] && 'Z'>=sr[i] || 'a'<=sr[i] && 'z'>=sr[i] ) {
a++ ;
}else if('0'<=sr[i] && '9'>=sr[i]) {
b++ ;
}else if(sr[i] == ' ') {
c++ ;
}else {
d++ ;
}
}
System.out.println("字母的个数为：" + a);
System.out.println("数字的个数为：" + b);
System.out.println("空格的个数为：" + c);
System.out.println("其他字符的个数为：" + d);
}
}
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特殊性质数的判断。例如水仙花数、完数、素数的判断程序：
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public class Daffodil {
public static void main(String[] args) {
int sum=0, number;
for(number=100;number<=999;number++) {
int num1 = number%10;
int num10 = number/10%10;
int num100 = number/100%10;
sum = num1*num1*num1 + num10*num10*num10 + num100*num100*num100;
if(sum==number) {
System.out.println(number+"是水仙花数");
}
}
}
}
public class WanNumber {
public static void main(String[] args) {
int i;
for(int num=1;num<=1000;num++) {
int sum = 0;
for( i=1;i<num;i++) {
if(num%i==0) {
sum+=i;
}
}
if(num==sum) {
System.out.println(num);
}
}
}
}
public class PrimeDemo {
public static void main(String[] args){
System.out.println("请输入一个数");
Scanner sc = new Scanner(System.in);
int paime = sc.nextInt();
boolean t=true;
int i;
for (i=2;i<paime;i++)
{
if(paime%i==0)
{
t=false;
}
}
if(t)
{
System.out.println("是素数");
}
else
{
System.out.println("是素数");
}
}
}
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类的继承定义。声明几何形状类，类中定义几何形状的成员变量和方法，然后继承声明几何形状类，创建对象，并显示对象的相关信息。
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| import java.util.Scanner;
class GeometricObject {
private String col;
private boolean fil;
public GeometricObject() {
col = "white";
fil = false;
}
public GeometricObject(String col, boolean fil) {
this.col = col;
this.fil = fil;
}
public String getCol() {
return col;
}
public void setCol(String col) {
this.col = col;
}
public boolean isFil() {
return fil;
}
public void setFil(boolean fil) {
this.fil = fil;
}
}
class Triangle extends GeometricObject {
private double s1;
private double s2;
private double s3;
public Triangle() {
s1 = 1;
s2 = 1;
s3 = 1;
}
public Triangle(String col, boolean fil, double s1, double s2, double s3) {
super(col, fil);
this.s1 = s1;
this.s2 = s2;
this.s3 = s3;
}
public double gets() {
double p = (s1 + s2 + s3) / 2.0;
double s = p * (p - s1) * (p - s2) * (p - s3);
s = Math.sqrt(s);
return s;
}
public double getc() {
return s1 + s2 + s3;
}
public void tos()
{
String s="Triangle:\n"+"side1 = "+s1+" side2 = "+s2+" side3 = "+s3+"\n"
+"Color: "+getCol()+" and filled: "+isFil()+"\n"
+"The area is "+gets()+"\n"+"The perimeter is "+getc()+"\n";
System.out.println(s);
}
}
public class Main {
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
double a=sc.nextDouble();
double b=sc.nextDouble();
double c=sc.nextDouble();
String s=sc.next();
boolean f=sc.nextBoolean();
sc.close();
Triangle t=new Triangle(s,f,a,b,c);
t.tos();
}
}
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数组排序程序。编写输入整数序列、对输入的整数进行排序后输出的程序：
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class Array4{
public static void main(String[] args){
int[] Arr = new int[]{14,52,56,32,17};
printArray(Arr);
bubbleSort(Arr);
printArray(Arr);
}
public static void printArray(int[] arr){
System.out.print("[");
for(int x=0; x<arr.length; x++){
if(x!=arr.length-1)
System.out.print(arr[x]+",");
else
System.out.println(arr[x]+"]");
}
}
public static void swap(int[] arr, int a, int b){
int temp = arr[a];
arr[a] = arr[b];
arr[b] = temp;
}
public static void bubbleSort(int[] arr){
for(int x=0; x<arr.length-1; x++){
for(int y=0; y<arr.length-1-x;y++){
if(arr[y]>arr[y+1])
swap(arr,y+1,y);
}
}
}
}
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提取整数中每个数字的程序：
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| public class Test{
public String print(int num){
while(num>0){
System.out.print(num%10+"，");
num/=10;
}
}
public static void main(String [] args){
Test t = new Test();
t.print(12345);
}
}
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三、基于 Swing 和 AWT 的界面程序设计
两个顶级容器的应用：Frame(窗口)、Dialog(弹窗) ：
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| import java.awt.Button;
import java.awt.Color;
import java.awt.Dialog;
import java.awt.Frame;
import java.awt.Label;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
public class Test{
public static void main(String[] args) {
Myframe frame = new Myframe();
frame.init();
frame.compen();
}
}
class Myframe extends Frame{
private static final long serialVersionUID = -3005332394925719672L;
public Myframe() {
super("测试窗口");
}
public void init() {
super.setVisible(true);
super.setBounds(200, 200, 200, 200);
this.addWindowListener(new WindowAdapter() {
@Override
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
}
public void compen() {
Button button = new Button("按钮");
button.setSize(100, 100);
this.setLayout(null);;
this.add(button);
button.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
end();
}
});
}
public void end() {
new Mydialog(this,"测试弹窗").increase();
}
}
class Mydialog extends Dialog{
private static final long serialVersionUID = 1L;
public Mydialog(Frame owner,String title) {
super(owner,title);
setVisible(true);
setSize(100, 200);
setBackground(Color.BLUE);
setLocation(200, 300);
this.addWindowListener(new WindowAdapter() {
@Override
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
}
public void increase() {
Label label = new Label("这是一个文本框",1);
this.add(label);
}
}
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四、JavaApplet 下的图形处理
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| import java.awt.* ;
import java.applet.Applet ;
public class AppletImage extends Applet{
private Image img[] ;
private int index=0;
public void init(){
img=new Image[10];
int num ;
for(num=0;num<10;num++){
img[num]=getImage(getDocumentBase(),"T"+(num+1)+".gif") ;
}
}
public void start(){
}
public void paint(Graphics g){
g.drawImage(img[index],0,0,this) ;
index=++index%10 ;
repaint() ;
try{
Thread.sleep(500) ;
}catch(Exception e){
}
}
}
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五、Java 下的多线程程序设计
编写一个有两个线程的程序，第一个线程用来计算 1~100 之间的偶数及个数，第二个线程用来计算 1-100 之间的偶数及个数：
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| package experiment4;
class NumberRunnable implements Runnable{
private final int first;
NumberRunnable(int first){
this.first=first;
}
@Override
public void run() {
for (int i=first;i<=100;i+=2){
System.out.println(i+ " ");
}
System.out.println("结束！");
}
}
public class Exp4_1 {
public static void main(String[] args){
NumberRunnable runnable1 = new NumberRunnable(1);
NumberRunnable runnable2 = new NumberRunnable(2);
Thread thread_odd = new Thread(runnable1,"奇数线程");
Thread thread_even = new Thread(runnable2,"偶数线程");
thread_odd.start();
thread_even.start();
}
}
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