android - How do I get the CPU temperature?

Question

I know it's somehow possible to get the CPU's temperature because I downloaded an app that does it in an unrooted device. How is it done?

edit: The application is called A1 CPU Tool. I spent several days searching for an answer.

edit2: Here's the code I tried

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);
    Sensor TempSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_AMBIENT_TEMPERATURE);
    mSensorManager.registerListener(temperatureSensor, TempSensor, SensorManager.SENSOR_DELAY_FASTEST);
}

private SensorEventListener temperatureSensor = new SensorEventListener(){

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onSensorChanged(SensorEvent event) {
        // TODO Auto-generated method stub
        float temp = event.values[0];
        Log.i("sensor", "sensor temp = " + temp);
    }
};

Answer 1

Read the file from following paths (Since it is different for different devices) to get cpu temperature details from different devices, One of the path will return the needed file.

    "/sys/devices/system/cpu/cpu0/cpufreq/cpu_temp"             
    "/sys/devices/system/cpu/cpu0/cpufreq/FakeShmoo_cpu_temp"    
    "/sys/class/thermal/thermal_zone1/temp"                      
    "/sys/class/i2c-adapter/i2c-4/4-004c/temperature"            
    "/sys/devices/platform/tegra-i2c.3/i2c-4/4-004c/temperature" 
    "/sys/devices/platform/omap/omap_temp_sensor.0/temperature"  
    "/sys/devices/platform/tegra_tmon/temp1_input"               
    "/sys/kernel/debug/tegra_thermal/temp_tj"                   
    "/sys/devices/platform/s5p-tmu/temperature"                  
    "/sys/class/thermal/thermal_zone0/temp"                      
    "/sys/devices/virtual/thermal/thermal_zone0/temp"            
    "/sys/class/hwmon/hwmon0/device/temp1_input"                 
    "/sys/devices/virtual/thermal/thermal_zone1/temp"            
    "/sys/devices/platform/s5p-tmu/curr_temp"    

To read the file, I used:

RandomAccessFile reader = new RandomAccessFile("/sys/devices/system/cpu/cpu0/cpufreq/cpu_temp", "r");
String line = reader.readLine();

Here is the another way: Read system files