Persistence: storing and showing game scores
/*
* RMSGameScores.java
* Copyright (c) 2000 Sun Microsystems, Inc. All Rights Reserved.
*
* Author: Srikanth Raju
*
* This software is the confidential and proprietary information of Sun
* Microsystems, Inc. ("Confidential Information"). You shall not
* disclose such Confidential Information and shall use it only in
* accordance with the terms of the license agreement you entered into
* with Sun.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
* SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
* PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
* SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
* THIS SOFTWARE OR ITS DERIVATIVES.
*/
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;
import javax.microedition.rms.RecordComparator;
import javax.microedition.rms.RecordEnumeration;
import javax.microedition.rms.RecordFilter;
import javax.microedition.rms.RecordStore;
import javax.microedition.rms.RecordStoreException;
/**
* A class used for storing and showing game scores.
*/
public class RMSGameScores extends MIDlet implements RecordFilter,
RecordComparator {
/*
* The RecordStore used for storing the game scores.
*/
private RecordStore recordStore = null;
/*
* The player name to use when filtering.
*/
public static String playerNameFilter = null;
/**
* The constuctor opens the underlying record store, creating it if
* necessary.
*/
public RMSGameScores() {
// Create a new record store for this example
try {
recordStore = RecordStore.openRecordStore("scores", true);
} catch (RecordStoreException rse) {
System.out.println("Record Store Exception in the ctor." + rse);
rse.printStackTrace();
}
}
/**
* startApp()
*/
public void startApp() throws MIDletStateChangeException {
RMSGameScores rmsgs = new RMSGameScores();
rmsgs.addScore(100, "Alice");
rmsgs.addScore(120, "Bill");
rmsgs.addScore(80, "Candice");
rmsgs.addScore(40, "Dean");
rmsgs.addScore(200, "Ethel");
rmsgs.addScore(110, "Farnsworth");
rmsgs.addScore(220, "Alice");
RMSGameScores.playerNameFilter = "Alice";
System.out
.println("Print all scores followed by Scores for Farnsworth");
rmsgs.printScores();
}
/*
* Part of the RecordFilter interface.
*/
public boolean matches(byte[] candidate) throws IllegalArgumentException {
// If no filter set, nothing can match it.
if (this.playerNameFilter == null) {
return false;
}
ByteArrayInputStream bais = new ByteArrayInputStream(candidate);
DataInputStream inputStream = new DataInputStream(bais);
String name = null;
try {
int score = inputStream.readInt();
name = inputStream.readUTF();
} catch (EOFException eofe) {
System.out.println(eofe);
eofe.printStackTrace();
} catch (IOException eofe) {
System.out.println(eofe);
eofe.printStackTrace();
}
return (this.playerNameFilter.equals(name));
}
/*
* Part of the RecordComparator interface.
*/
public int compare(byte[] rec1, byte[] rec2) {
// Construct DataInputStreams for extracting the scores from
// the records.
ByteArrayInputStream bais1 = new ByteArrayInputStream(rec1);
DataInputStream inputStream1 = new DataInputStream(bais1);
ByteArrayInputStream bais2 = new ByteArrayInputStream(rec2);
DataInputStream inputStream2 = new DataInputStream(bais2);
int score1 = 0;
int score2 = 0;
try {
// Extract the scores.
score1 = inputStream1.readInt();
score2 = inputStream2.readInt();
} catch (EOFException eofe) {
System.out.println(eofe);
eofe.printStackTrace();
} catch (IOException eofe) {
System.out.println(eofe);
eofe.printStackTrace();
}
// Sort by score
if (score1 > score2) {
return RecordComparator.FOLLOWS;
} else if (score1 < score2) {
return RecordComparator.PRECEDES;
} else {
return RecordComparator.EQUIVALENT;
}
}
/**
* Add a new score to the storage.
*
* @param score
* the score to store.
* @param playerName
* the name of the play achieving this score.
*/
public void addScore(int score, String playerName) {
// Each score is stored in a separate record, formatted with
// the score, followed by the player name.
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream outputStream = new DataOutputStream(baos);
try {
// Push the score into a byte array.
outputStream.writeInt(score);
// Then push the player name.
outputStream.writeUTF(playerName);
} catch (IOException ioe) {
System.out.println(ioe);
ioe.printStackTrace();
}
// Extract the byte array
byte[] b = baos.toByteArray();
try {
// Add it to the record store
recordStore.addRecord(b, 0, b.length);
} catch (RecordStoreException rse) {
System.out.println(rse);
rse.printStackTrace();
}
}
/**
* A helper method for the printScores methods.
*/
private void printScoresHelper(RecordEnumeration re) {
try {
while (re.hasNextElement()) {
int id = re.nextRecordId();
ByteArrayInputStream bais = new ByteArrayInputStream(
recordStore.getRecord(id));
DataInputStream inputStream = new DataInputStream(bais);
try {
int score = inputStream.readInt();
String playerName = inputStream.readUTF();
System.out.println(playerName + " = " + score);
} catch (EOFException eofe) {
System.out.println(eofe);
eofe.printStackTrace();
}
}
} catch (RecordStoreException rse) {
System.out.println(rse);
rse.printStackTrace();
} catch (IOException ioe) {
System.out.println(ioe);
ioe.printStackTrace();
}
}
/**
* This method prints all of the scores sorted by game score.
*/
public void printScores() {
try {
// Enumerate the records using the comparator implemented
// above to sort by game score.
// No RecordFilter here. All records in the RecordStore
RecordEnumeration re = recordStore.enumerateRecords(null, this,
true);
// Print all scores
System.out.println("Print all scores...");
printScoresHelper(re);
// Enumerate records respecting a RecordFilter
re = recordStore.enumerateRecords(this, this, true);
//Print scores for Farnsworth
System.out.println("Print scores for : " + this.playerNameFilter);
printScoresHelper(re);
} catch (RecordStoreException rse) {
System.out.println(rse);
rse.printStackTrace();
}
}
/**
* pauseApp()
*/
public void pauseApp() {
System.out.println("pauseApp()");
}
/**
* destroyApp()
*
* This closes our open RecordStore when we are destroyed.
*
* @param cond
* true if this is an unconditional destroy false if it is not
* (ignored here and treated as unconditional)
*/
public void destroyApp(boolean cond) {
System.out.println("destroyApp( )");
try {
if (recordStore != null)
recordStore.closeRecordStore();
} catch (Exception ignore) {
// ignore this
}
}
}
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