import java.util.Date;  
public  class Test extends Date{  
public static void main(String[] args) {  
    new Test().test();  
}  
public void test(){  
    System.out.println(super.getClass().getName());  
}  
}  

public static void main(String[] args) {

    String str = new String("adcdefg");
    char[] chars = {'s', 'd', 'f'};
    process(str, chars);
    System.out.println(str);
    System.out.println(chars);

}

private static void process(String str, char[] chars) {
    str = "fsdf";
    chars[0] = 'a';
}

adcdefg
adf

    String s1 = "abc";
    String s2 = "abc";
    String s3 = new String("abc");//创建两个String对象，堆中创建一个String对象指向String常量池中的abc(如果存在就不在新建）
    String s4 = s1.intern();//从String常量池寻找一个String，和s1 equals返回true
    String s5 = s3.intern();//从String常量池寻找
    System.out.println("s1==s2:" + (s1 == s2));
    System.out.println("s1==s3:" + (s1 == s3));
    System.out.println("s1==s4:" + (s1 == s4));
    System.out.println("s1==s5:" + (s1 == s5));

s1==s2:true
s1==s3:false
s1==s4:true
s1==s5:true

    String a = "a";
    String a1 = new String("a");
    String a2 = a1.trim() + "";
    String a3 = "a" + "";
    String a4 = "a".trim() + "";
    System.out.println(a == a1);
    System.out.println(a.intern() == a1.intern());
    System.out.println(a2 == a1);
    System.out.println(a3 == a);
    System.out.println(a4 == a);

false
true
false
true
false

StringBuffer sbf = new StringBuffer();    
for(int i=0;i<100;i++)  
{  
    sbf.append(i);  
}

String str = new String();    
for(int i=0;i<100;i++)  
{  
    str = str + i;  
}

// Register ourselves with the DriverManager
//
static {
    try {
        java.sql.DriverManager.registerDriver(new Driver());
    } catch (SQLException E) {
    throw new RuntimeException("Can't register driver!");
    }
}

$ adb shell dumpsys batterystats > xxx.txt  //得到整个设备的电量消耗信息
$ adb shell dumpsys batterystats > com.package.name > xxx.txt //得到指定app相关的电量消耗信息

$ python historian.py xxx.txt > xxx.html

// It is very easy to subscribe to changes to the battery state, but you can get the current
// state by simply passing null in as your receiver.  Nifty, isn't that?
IntentFilter filter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
Intent batteryStatus = this.registerReceiver(null, filter);
int chargePlug = batteryStatus.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
boolean acCharge = (chargePlug == BatteryManager.BATTERY_PLUGGED_AC);
if (acCharge) {
    Log.v(LOG_TAG,“The phone is charging!”);
}

/**
 * This method checks for power by comparing the current battery state against all possible
 * plugged in states. In this case, a device may be considered plugged in either by USB, AC, or
 * wireless charge. (Wireless charge was introduced in API Level 17.)
 */
private boolean checkForPower() {
// It is very easy to subscribe to changes to the battery state, but you can get the current
// state by simply passing null in as your receiver.  Nifty, isn't that?
IntentFilter filter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
Intent batteryStatus = this.registerReceiver(null, filter);

// There are currently three ways a device can be plugged in. We should check them all.
int chargePlug = batteryStatus.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
boolean usbCharge = (chargePlug == BatteryManager.BATTERY_PLUGGED_USB);
boolean acCharge = (chargePlug == BatteryManager.BATTERY_PLUGGED_AC);
boolean wirelessCharge = false;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
    wirelessCharge = (chargePlug == BatteryManager.BATTERY_PLUGGED_WIRELESS);
}
return (usbCharge || acCharge || wirelessCharge);
}

public class MyJobService extends JobService {
private static final String LOG_TAG = "MyJobService";

@Override
public void onCreate() {
    super.onCreate();
    Log.i(LOG_TAG, "MyJobService created");
}

@Override
public void onDestroy() {
    super.onDestroy();
    Log.i(LOG_TAG, "MyJobService destroyed");
}

@Override
public boolean onStartJob(JobParameters params) {
    // This is where you would implement all of the logic for your job. Note that this runs
    // on the main thread, so you will want to use a separate thread for asynchronous work
    // (as we demonstrate below to establish a network connection).
    // If you use a separate thread, return true to indicate that you need a "reschedule" to
    // return to the job at some point in the future to finish processing the work. Otherwise,
    // return false when finished.
    Log.i(LOG_TAG, "Totally and completely working on job " + params.getJobId());
    // First, check the network, and then attempt to connect.
    if (isNetworkConnected()) {
        new SimpleDownloadTask() .execute(params);
        return true;
    } else {
        Log.i(LOG_TAG, "No connection on job " + params.getJobId() + "; sad face");
    }
    return false;
}

@Override
public boolean onStopJob(JobParameters params) {
    // Called if the job must be stopped before jobFinished() has been called. This may
    // happen if the requirements are no longer being met, such as the user no longer
    // connecting to WiFi, or the device no longer being idle. Use this callback to resolve
    // anything that may cause your application to misbehave from the job being halted.
    // Return true if the job should be rescheduled based on the retry criteria specified
    // when the job was created or return false to drop the job. Regardless of the value
    // returned, your job must stop executing.
    Log.i(LOG_TAG, "Whelp, something changed, so I'm calling it on job " + params.getJobId());
    return false;
}

/**
 * Determines if the device is currently online.
 */
private boolean isNetworkConnected() {
    ConnectivityManager connectivityManager =
            (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
    return (networkInfo != null && networkInfo.isConnected());
}

/**
 *  Uses AsyncTask to create a task away from the main UI thread. This task creates a
 *  HTTPUrlConnection, and then downloads the contents of the webpage as an InputStream.
 *  The InputStream is then converted to a String, which is logged by the
 *  onPostExecute() method.
 */
private class SimpleDownloadTask extends AsyncTask<JobParameters, Void, String> {

    protected JobParameters mJobParam;

    @Override
    protected String doInBackground(JobParameters... params) {
        // cache system provided job requirements
        mJobParam = params[0];
        try {
            InputStream is = null;
            // Only display the first 50 characters of the retrieved web page content.
            int len = 50;

            URL url = new URL("https://www.google.com");
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(10000); //10sec
            conn.setConnectTimeout(15000); //15sec
            conn.setRequestMethod("GET");
            //Starts the query
            conn.connect();
            int response = conn.getResponseCode();
            Log.d(LOG_TAG, "The response is: " + response);
            is = conn.getInputStream();

            // Convert the input stream to a string
            Reader reader = null;
            reader = new InputStreamReader(is, "UTF-8");
            char[] buffer = new char[len];
            reader.read(buffer);
            return new String(buffer);

        } catch (IOException e) {
            return "Unable to retrieve web page.";
        }
    }

    @Override
    protected void onPostExecute(String result) {
        jobFinished(mJobParam, false);
        Log.i(LOG_TAG, result);
    }
}
}

public class FreeTheWakelockActivity extends ActionBarActivity {
public static final String LOG_TAG = "FreeTheWakelockActivity";

TextView mWakeLockMsg;
ComponentName mServiceComponent;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_wakelock);

    mWakeLockMsg = (TextView) findViewById(R.id.wakelock_txt);
    mServiceComponent = new ComponentName(this, MyJobService.class);
    Intent startServiceIntent = new Intent(this, MyJobService.class);
    startService(startServiceIntent);

    Button theButtonThatWakelocks = (Button) findViewById(R.id.wakelock_poll);
    theButtonThatWakelocks.setText(R.string.poll_server_button);

    theButtonThatWakelocks.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
                pollServer();
        }
    });
}

/**
 * This method polls the server via the JobScheduler API. By scheduling the job with this API,
 * your app can be confident it will execute, but without the need for a wake lock. Rather, the
 * API will take your network jobs and execute them in batch to best take advantage of the
 * initial network connection cost.
 *
 * The JobScheduler API works through a background service. In this sample, we have
 * a simple service in MyJobService to get you started. The job is scheduled here in
 * the activity, but the job itself is executed in MyJobService in the startJob() method. For
 * example, to poll your server, you would create the network connection, send your GET
 * request, and then process the response all in MyJobService. This allows the JobScheduler API
 * to invoke your logic without needed to restart your activity.
 *
 * For brevity in the sample, we are scheduling the same job several times in quick succession,
 * but again, try to consider similar tasks occurring over time in your application that can
 * afford to wait and may benefit from batching.
 */
public void pollServer() {
    JobScheduler scheduler = (JobScheduler) getSystemService(Context.JOB_SCHEDULER_SERVICE);
    for (int i=0; i<10; i++) {
        JobInfo jobInfo = new JobInfo.Builder(i, mServiceComponent)
                .setMinimumLatency(5000) // 5 seconds
                .setOverrideDeadline(60000) // 60 seconds (for brevity in the sample)
                .setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY) // WiFi or data connections
                .build();

        mWakeLockMsg.append("Scheduling job " + i + "!\n");
        scheduler.schedule(jobInfo);
    }
}
}

private static void printRhomb(int n) {
    if (n % 2 == 0) {
        return;
    }
    int[][] postions = new int[n][n];
    int mid = n / 2;
    for (int i = 0, low = mid, high = mid; i < postions.length; i++) {
        int[] row = postions[i];
        for (int j = 0; j < row.length; j++) {
            if (j >= low && j <= high)
                row[j] = 1;
            if (row[j] == 1) {
                System.out.print('*');
            } else {
                System.out.print(" ");
            }
        }
        if (i < mid) {
            low--;
            high++;
        } else {
            low++;
            high--;
        }
        System.out.println();
    }
}

     *     
    ***    
   *****   
  *******  
 ********* 
***********
 ********* 
  *******  
   *****   
    ***    
     * 

if (res < WindowManagerGlobal.ADD_OKAY) {
                mAttachInfo.mRootView = null;
                mAdded = false;
                mFallbackEventHandler.setView(null);
                unscheduleTraversals();
                setAccessibilityFocus(null, null);
                switch (res) {
                    case WindowManagerGlobal.ADD_BAD_APP_TOKEN:
                    case WindowManagerGlobal.ADD_BAD_SUBWINDOW_TOKEN:
                        throw new WindowManager.BadTokenException(
                                "Unable to add window -- token " + attrs.token
                                + " is not valid; is your activity running?");
                    case WindowManagerGlobal.ADD_NOT_APP_TOKEN:
                        throw new WindowManager.BadTokenException(
                                "Unable to add window -- token " + attrs.token
                                + " is not for an application");

public class Printrhomb {

private int outInt;

public static void main(String[] args) {
    InnerClass innerClass = new Printrhomb().new InnerClass();
}

class InnerClass {
    public void test() {
        System.out.println(outInt);
    }
}
}

07-22 15:25:46.830 2339-2339/com.example.android.displayingbitmaps E/JavaBinder: !!! FAILED BINDER TRANSACTION !!!
07-22 15:27:59.341 2339-2339/com.example.android.displayingbitmaps E/JavaBinder: !!! FAILED BINDER TRANSACTION !!!