我正在启动Java类，这是我的第一个代码，所以请保持温和;）
//importing libraries
import java.io.*;
import javax.swing.*;
public class SongCollection {//class
//declaring arrays to hold user inputs
static String title[]={"","",""};
static String artist[]={"","",""};
static double length[]={0,0,0};
static int arrayindex=0;//declaring an index to keep track of arrays
public static void main(String[] args) throws IOException{//main method
menu();//calling menu method
}
public static void menu() throws IOException{//menu method
String s=JOptionPane.showInputDialog("Choose a menu option\n" +//taking user input and storing it into a string
"1: Add Song\n" +
"2: Search for a song\n" +
"3: Edit a song\n" +
"4: Sort songs\n" +
"5: Print songs\n" +
"6: Save songs to file\n" +
"7: Read songs from file\n" +
"8: Exit");
int menu=Integer.parseInt(s);//converting user input into a number
switch(menu){//going to the appropriate method depending on what number the user presses on the keyboard
case 1: add(); break;
case 2: search(); break;
case 3: edit(); break;
case 4: sort(); break;
case 5: print(); break;
case 6: tofile(); break;
case 7: fromfile(); break;
case 8: System.exit(0); break;
default: JOptionPane.showMessageDialog(null,"Please choose a valid option"); break;
}
}
public static void add() throws IOException{//add method
if(arrayindex>=title.length){//checking if the array is full
JOptionPane.showMessageDialog(null,"Song collection is full");
menu();
}
//taking the user input and storing them into variables
String newtitle=JOptionPane.showInputDialog("Enter the song title:");
String newartist=JOptionPane.showInputDialog("Enter the artist of the song:");
String s=JOptionPane.showInputDialog("Enter the length of the song:");
double newlength=Double.parseDouble(s);//converting length into a number
//taking the variables and storing them in the arrays
title[arrayindex]=newtitle;
artist[arrayindex]=newartist;
length[arrayindex]=newlength;
arrayindex+=1;//incrementing one to the array index because one new entry was added
menu();
}
public static void search() throws IOException{//search method
String key=JOptionPane.showInputDialog("Enter your search key: ");//taking in the users search key
for(int i=0; i<title.length; i++){
if(key.equals(title[i]) || key.equals(artist[i]) || key.equals(length[i])){//checking if the key is in any of the arrays
JOptionPane.showMessageDialog(null,title[i]+", "+artist[i]+", "+length[i]);//printing out the found key
menu();
}
}
JOptionPane.showMessageDialog(null,"Key not found");//if the loop completes the key doesnt exist
}
public static void edit() throws IOException{//edit method
String s=JOptionPane.showInputDialog("Which entry do you want to edit. Enter a whole number between 0 and " + (arrayindex-1));//asking the user which entry they want to edit
int edit=Integer.parseInt(s);//converting user input into a number
if(edit>arrayindex || edit<0){//checking if they enter a valid entry that can be editted
JOptionPane.showMessageDialog(null,"The entry you entered is does not exist");
menu();
}
//taking new entries from the user
String newtitle=JOptionPane.showInputDialog("Enter the new song title:");
String newartist=JOptionPane.showInputDialog("Enter the new artist of the song:");
String s2=JOptionPane.showInputDialog("Enter the new length of the song:");
double newlength=Double.parseDouble(s2);
//storing them into the array replacing what was previously stored in that index
title[edit]=newtitle;
artist[edit]=newartist;
length[edit]=newlength;
menu();
}
public static void sort(){//sort method
//nested loop to loop through all elements and make swap when needed
for(int i=0; i<title.length-1; i++)
{
for (int i1=0; i1<title.length-1; i1++)
{
//storing title current index and title next into 2 different variables
String t1 = title[i1];
String t2 = title[i1 + 1];
//storing artist current index and artist next index into 2 different variables
String a1 = artist[i1];
String a2 = artist[i1 + 1];
//storing length current index and length next index into 2 different variables
double l1 = length[i1];
double l2 = length[i1 + 1];
//comparing title current index with title next index using the compareto method
if ((t1).compareTo(t2) > 0)
{
//creating a temporary variable to store the first variable and then swapping the 2 around
String t3 = t1;
title[i1] = t2;
title[i1 + 1] = t3;
String a3 = a1;
artist[i1] = a2;
artist[i1 + 1] = a3;
Double l3 = l1;
length[i1] = l2;
length[i1 + 1] = l3;
}
}
}
}
public static void print() throws IOException{//print method
//looping through and printing out each element
for(int i=0; i<title.length; i++)
{
JOptionPane.showMessageDialog(null,title[i]+","+artist[i]+","+length[i]);
}
menu();
}
public static void tofile() throws IOException{//tofile method
final FileWriter fw=new FileWriter("SongCollection.txt");//declaring filewriter
final BufferedWriter bw=new BufferedWriter(fw);//delcaring buffer
final PrintWriter pw=new PrintWriter(bw);//declaring print writer
//looping through array
for(int i=0; i<title.length; i++)
{
pw.println(title[i]+","+artist[i]+","+length[i]);//using print writer to write all 3 elements on one line
}
pw.close();//closing the writer
menu();
}
public static void fromfile() throws IOException{//from file method
final FileReader inf=new FileReader("SongCollection.txt");//declaring file reader
final BufferedReader ib=new BufferedReader(inf);//declaring buffer reader
String s;//string to hold read lines from file
while((s=ib.readLine())!=null)//looping through the file while the lines are not empty
{
JOptionPane.showMessageDialog(null,s);//outputting the read in data to the screen
}
}
}
我有几个问题：
如何使添加歌曲界面有一个按钮返回主菜单？类似于其他接口？
答案 0 :(得分：4)
这是一个典型的新手错误：你的课程做得太多了。稍微分解一下。
有一个将事物封装在一起的Song类：
package model;
public class Song {
private String title;
private String author;
private int length;
// You add the rest.
}
不要使用基元数组;请改用Java collections。
从模型类中分离UI内容。可以在不重写所有代码的情况下更改UI。
答案 1 :(得分：2)
你真的应该使用Vector或ArrayList，而不是那些String []数组。否则，你基本上说用户不可能输入三个以上的输入。即使他们可以，你要么必须调整你的数组大小，要么你会有阵列出现异常。
通过声明一个Vector或ArrayList，你可以继续添加元素（虽然你仍然有可用的内存），它可以防止数组超出你可能用原始字符串数组引起的异常。