我不断收到ClassCastException
线程“main”中的异常java.lang.ClassCastException：java.lang.String无法强制转换为homework5.Creature
at ho.Creature.compareTo(Creature.java:11)
at java.util.Collections.indexedBinarySearch(Collections.java:215)
at java.util.Collections.binarySearch(Collections.java:201)
at ho.PC.play(PC.java:61)
at ho.Main.main(Main.java:41)
Java结果：1
我不确定我还需要提供哪些信息
方法我必须开始：
public void play(PC pc) {
Scanner reader = new Scanner(System.in);
while (true) {
String command = reader.nextLine();
String[] commands = null;
if (command.contains(":")) {
commands = command.split(":");
ArrayList array = getRoom().getCreatures();
Collections.sort(array);
int index = Collections.binarySearch(array, commands[0]);
Creature c = getRoom().getCreatures().get(index);
//Creature c = getRoom().binarySearchForCreature(commands[0], 0, getRoom().getCount() - 1);
if (c != null) {
if (commands[1].equalsIgnoreCase("clean")) {
c.clean(pc);
pc.getRoom().critReactRoomStateChange("clean", pc, c.getName());
} else if (commands[1].equalsIgnoreCase("dirty")) {
c.dirty(pc);
pc.getRoom().critReactRoomStateChange("dirty", pc, c.getName());
} else if (commands[1].equalsIgnoreCase("n")) {
c.tryMove(commands[1], pc);
c.checkNewRoom();
} else if (commands[1].equalsIgnoreCase("e")) {
c.tryMove(commands[1], pc);
c.checkNewRoom();
} else if (commands[1].equalsIgnoreCase("s")) {
c.tryMove(commands[1], pc);
c.checkNewRoom();
} else if (commands[1].equalsIgnoreCase("w")) {
c.tryMove(commands[1], pc);
c.checkNewRoom();
} else {
System.out.println("Command Does not exist.");
}
} else {
System.out.println("That creature is not in the room.");
} ...(Keeps going)
实现Collections.binarySearch后，我开始收到此错误 我在我的生物课上得到了错误。 这是顶级错误来自的类 ho.Creature.compareTo（Creature.java:11）compareTo接近底部。
public abstract class Creature implements Comparable<Creature> {
protected Room roomRef;
private String name;
private String descript;
public Creature(String name, String descript) {
this.name = name;
this.descript = descript;
}
public void setRoom(Room roomRef) {
this.roomRef = roomRef;
}
public Room getRoom() {
return this.roomRef;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public final void clean(PC pc) {
String cClass = "";
if (!getRoom().getState().equalsIgnoreCase("clean")) {
if (getRoom().getState().equalsIgnoreCase("dirty")) {
getRoom().setState("half-dirty");
} else {
getRoom().getState().equalsIgnoreCase("half-dirty");
getRoom().setState("clean");
}
if (this instanceof Animal) {
cClass = "Animal";
System.out.println(getName() + " the " + cClass + " cleans the room " + roomRef.getName() + ". The room's state is now " + roomRef.getState());
reactG(pc);
reactG(pc);
reactG(pc);
}
if (this instanceof NPC) {
cClass = "NPC";
System.out.println(getName() + " the " + cClass + " cleans the room " + roomRef.getName() + ". The room's state is now " + roomRef.getState());
reactD(pc);
reactD(pc);
reactD(pc);
}
if (this instanceof PC) {
cClass = "PC";
}
} else {
System.out.println("The room " + roomRef.getName() + "is already clean.");
}
}
public final void dirty(PC pc) {
String cClass = "";
if (!getRoom().getState().equalsIgnoreCase("dirty")) {
if (getRoom().getState().equalsIgnoreCase("clean")) {
getRoom().setState("half-dirty");
} else {
getRoom().getState().equalsIgnoreCase("half-drity");
getRoom().setState("dirty");
}
if (this instanceof Animal) {
cClass = "Animal";
System.out.println(getName() + " the " + cClass + " dirties the room " + roomRef.getName() + ". The room's state is now " + roomRef.getState());
reactD(pc);
reactD(pc);
reactD(pc);
}
if (this instanceof NPC) {
cClass = "NPC";
System.out.println(getName() + " the " + cClass + " dirties the room " + roomRef.getName() + ". The room's state is now " + roomRef.getState());
reactG(pc);
reactG(pc);
reactG(pc);
}
if (this instanceof PC) {
cClass = "PC";
System.out.println(getName() + " the " + cClass + " dirties the room " + roomRef.getName() + ". The room's state is now " + roomRef.getState());
}
} else {
System.out.println("The room " + roomRef.getName() + "is already dirty.");
}
}
public String getCreatureType() {
if ((this instanceof PC)) {
return "PC";
}
if ((this instanceof NPC)) {
return "NPC";
}
if ((this instanceof Animal)) {
return "Animal";
}
return null;
}
public void reactStateChange(String command, PC pc) {
if ((this instanceof NPC)) {
if (command.equals("clean")) {
reactD(pc);
}
if (command.equals("dirty")) {
reactG(pc);
}
if (this.roomRef.getState().equalsIgnoreCase("clean")) {
tryLeaveRoom(pc);
}
}
if (this instanceof Animal) {
if (command.equalsIgnoreCase("clean")) {
reactG(pc);
}
if (command.equals("dirty")) {
reactD(pc);
}
if (this.roomRef.getState().equalsIgnoreCase("dirty")) {
tryLeaveRoom(pc);
}
}
}
public void checkNewRoom() {
if ((this instanceof NPC)) {
if (this.roomRef.getState().equalsIgnoreCase("clean")) {
this.roomRef.setState("half-dirty");
}
}
if (this instanceof Animal) {
if (this.roomRef.getState().equalsIgnoreCase("dirty")) {
this.roomRef.setState("half-dirty");
}
}
}
public void tryMove(String direction, PC pc) {
try {
Room dest = getRoom().getNeighbor(direction);
if (dest.getCreatures().size() <= 9) {
getRoom().removeCreature(this);
setRoom(getRoom().getNeighbor(direction));
dest.addCreature(this);
System.out.println("The "
+ getCreatureType() + " "
+ getName() + " left the room and goes to "
+ dest.getName() + " through the "
+ changeDirectionName(direction) + " door.");
} else {
System.out.println("Cannot move "
+ changeDirectionName(direction)
+ " to the room " + getRoom().getNeighbor(direction).getName()
+ " because it is full!");
reactD(pc);
}
} catch (NullPointerException e) {
System.out.println("There is not a neighbor to the " + changeDirectionName(direction) + "!");
reactD(pc);
}
}
private String changeDirectionName(String ref) {
if (ref.equalsIgnoreCase("n")) {
ref = "north";
return ref;
}
if (ref.equalsIgnoreCase("s")) {
ref = "south";
return ref;
}
if (ref.equalsIgnoreCase("e")) {
ref = "east";
return ref;
}
if (ref.equalsIgnoreCase("w")) {
ref = "west";
return ref;
}
return null;
}
public void tryLeaveRoom(PC pc) {
boolean allChosen = false;
boolean[] chosen = new boolean[4];
while (allChosen == false) {
String[] directions = {"n", "e", "s", "w"};
Random dirPick = new Random();
int rNum = dirPick.nextInt(4);
String direction = directions[rNum];
Room destRoom = getRoom().getNeighbor(direction);
if (chosen[rNum] == false) {
if (destRoom != null) {
tryMove(direction, pc);
break;
}
chosen[rNum] = true;
}
if (chosen[0] == true && chosen[1] == true && chosen[2] == true && chosen[3] == true) {
allChosen = true;
getRoom().removeCreature(this);
getRoom().roofAction(pc);
System.out.println("The " + getCreatureType() + " " + getName() + "leaves through the roof of " + getRoom().getName());
}
}
}
protected abstract void reactRoom(PC pc);
protected abstract void reactG(PC pc);
protected abstract void reactD(PC pc);
public void look() {
String creatureS = "";
System.out.print("The name of the room you are in is " + roomRef.getName() + ". ");
System.out.print("\nDescription: " + roomRef.getDescription() + " ");
System.out.print("and it's state is " + roomRef.getState() + ".\n");
System.out.print("It contains the creatures: \n");
for (int i = 0; i < roomRef.getCreatures().size(); i++) {
creatureS += "\t" + roomRef.getCreatures().get(i).getName()+ "\n";
}
// for (int i = 0; i < roomRef.getCreatures().length; i++) {
// if (this.roomRef.getCreatures()[i] != null) {
// creatureS += "\t" + roomRef.getCreatures()[i] + "\n";
// }
// }
System.out.println(creatureS);
System.out.print("Neighbors:\n");
if (this.roomRef.getNeighbor("n") != null) {
System.out.print("\tThe north door is: " + this.roomRef.getNorthD().getName() + "\n");
} else {
System.out.print("");
}
if (this.roomRef.getNeighbor("s") != null) {
System.out.print("\tThe south door is: " + this.roomRef.getSouthD().getName() + "\n");
} else {
System.out.print("");
}
if (this.roomRef.getNeighbor("e") != null) {
System.out.print("\tThe east door is: " + this.roomRef.getEastD().getName() + "\n");
} else {
System.out.print("");
}
if (this.roomRef.getNeighbor("w") != null) {
System.out.print("\tThe west door is: " + this.roomRef.getWestD().getName() + "\n");
} else {
System.out.print("");
}
}
public int compareTo(Creature o) {
return this.getName().compareToIgnoreCase(o.getName());
}
public String toString() {
return name + " is a/an " + this.getCreatureType() + " who is " + descript;
}
}
答案 0 :(得分：4)
在致电binarySearch()时，密钥为String，但类型为Creature。
public static int binarySearch(List list,
Object key)
抛出：ClassCastException - 如果是 list包含不包含的元素 相互比较（例如， 字符串和整数），或搜索 关键在于不能相互比较 列表的元素。
答案 1 :(得分：1)
你有：
int index = Collections.binarySearch(array, commands[0]);
array是Creature个对象的列表。 commands[0]是String个对象。
你做不到。它会尝试将String投射到Creature并获得您的例外。
您必须为搜索提供Creature，而不是String。您在Comparable.compareTo()中的Creature实施用于确定匹配。