Question

我创建了两个文件，一个带有如下界面：

       public interface ICharQ {
       void put(char ch);
       char get();
       }

和实现类如下：

    //A fixed size Queue class for characters

    class FixedQueue implements ICharQ{
    private char q[]; //This queue holds the characters
    private int putloc, getloc; //the put and get indices

    public FixedQueue(int size){
    q = new char[size+1]; //allocate memory for the queue
    putloc = getloc = 0;
}

    //Put a character into the queue
    public void put(char ch){
    if(putloc == q.length - 1){
    System.out.println(" - Queue is full");
    return;
    }
    putloc++;
    q[putloc] = ch;
}

    //Get a character from the Queue
    public char get(){
    if(getloc == putloc){
    System.out.println(" - Queue is empty");
    return (char) 0;
    }
    getloc++;
    return q[getloc];
}
}

    //A circular Queue
    class CircularQueue implements ICharQ{
    private char q[]; //This queue holds the characters
    private int putloc, getloc; //the put and get indices

    public CircularQueue(int size){
    q = new char[size+1]; //allocate memory for the queue
    putloc = getloc = 0;
}

    //Put a character into the queue
    public void put(char ch){
    /*Queue is full if putloc is one less than getloc or if putloc is at the    end and getloc is at the beginning */
    if((putloc + 1 == getloc)|(putloc == q.length-1 & getloc == 0)){
    System.out.println(" - Queue is full");
    return;
    }
    putloc++;
    if(putloc == q.length) putloc = 0; //reset loop
    q[putloc] = ch;
}

    //Get character from the Queue
    public char get(){
    if(getloc == putloc){
    System.out.println(" - Queue is empty");
    return (char) 0;
    }
    getloc++;
    if(getloc == q.length) getloc = 0;
    return q[getloc];
}
}


    //A dynamic Queue
    class DynQueue implements ICharQ {
    private char q[]; // this array holds the queue
    private int putloc, getloc; // the put and get indices
    // Construct an empty queue given its size.
    public DynQueue(int size) {
    q = new char[size+1]; // allocate memory for queue
    putloc = getloc = 0;
}

    //put a character into the queue
    public void put(char ch){
    if(putloc == q.length-1){
    //increase queue size
    char t[] = new char[q.length * 2];

    //copy elements into the new queue
    for(int i=0; i<q.length; i++)
    t[i] = q[i];
    q = t;
    }
    putloc++;
    q[putloc] = ch;
}

// Get a character from the queue.
    public char get() {
    if(getloc == putloc) {
    System.out.println(" – Queue is empty.");
    return (char) 0;
    }
    getloc++;
    return q[getloc];
}
    }

    //Demonstrate the ICharQ interface
    class IQDemo{
    public static void main(String args[]){
    FixedQueue q1 = new FixedQueue(10);
    DynQueue q2 = new DynQueue(5);
    CircularQueue q3 = new CircularQueue(10);

    ICharQ iQ;
    char ch;
    int i;

    iQ = q1;
    //Put some characters into the fixed queue
    for(i = 0; i<10; i++){
    iQ.put((char)('A' + i));
    }
    //Show the queue
    for(i=0; i<10; i++){
    System.out.print("Contents of fixed queue: ");
    for(i=0; i < 10; i++) {
    ch = iQ.get();
    System.out.print(ch);
    }
    }
    System.out.println();
    iQ = q2;
    // Put some characters into dynamic queue.
    for(i=0; i < 10; i++)
    iQ.put((char) ('Z' - i));
    // Show the queue.
    System.out.print("Contents of dynamic queue: ");
    for(i=0; i < 10; i++) {
    ch = iQ.get();
    System.out.print(ch);
    }
    System.out.println();
    iQ = q3;
    // Put some characters into circular queue.
    for(i=0; i < 10; i++)
    iQ.put((char) ('A' + i));
    // Show the queue.
    System.out.print("Contents of circular queue: ");
    for(i=0; i < 10; i++) {
    ch = iQ.get();
    System.out.print(ch);
    }
    System.out.println();

    // Put more characters into circular queue.
    for(i=10; i < 20; i++)
    iQ.put((char) ('A' + i));
    // Show the queue.
    System.out.print("Contents of circular queue: ");
    for(i=0; i < 10; i++) {
    ch = iQ.get();
    System.out.print(ch);
    }
    System.out.println("\nStore and consume from" +
    " circular queue.");
    // Use and consume from circular queue.
    for(i=0; i < 20; i++) {
    iQ.put((char) ('A' + i));
    ch = iQ.get();
    System.out.print(ch);
    }
}
}

现在文件位于同一目录中。 ICharQ.java文件编译得很好。但是当我尝试编译IQDemo.java时，它会发出错误，指出它无法找到ICharQ。

然而，当我从接口文件中删除公共访问器并在IQDemo中包含代码时，它完美地工作。但是，当我将其改为公开时，它并没有编译。

代码有什么问题，或者我错过了什么？请帮忙。

Answer 1

这听起来像路径和包的问题。检查类路径设置（cp命令行选项），确保在每个文件的顶部声明包，并将这些文件放在文件系统中。

您应该将package YourNick.YourProject;作为文件的第一行。然后使用javac -cp $CP $CP/YourNick/YourProject/{ICharQ,IQDemo}.java编译它们，并在ICharQ.class中创建生成的字节码文件（即IQDemo.class和$CP/YourNick/YourProject）。然后以java执行java -cp $CP YourNick.YourProject.IQDemo命令。

使用IDE时，项目的类路径设置和目录结构会以某种方式自动处理。您仍然需要选择包名称。

所以，这应该是结果（显示为shell会话）：

$ cd /home/chatterjee/java-projects
$ ls Queue
ICharQ.java    IQDemo.java
$ cat Queue/ICharQ.java
package Queue;
public interface ICharQ {
    void put(char ch);
    char get();
}
$ cat Queue/IQDemo.java
package Queue;
… lots of code …
$ javac -cp . ./Queue/{ICharQ,IQDemo}.java
$ ls Queue
ICharQ.class    ICharQ.java    IQDemo.class    IQDemo.java
$ java -cp . Queue.IQDemo
… desired output …

接口未正确实施

1 个答案: