How to get the build.prop values?

You can probably consider using SystemProperties.get("someKey") as suggested by @kangear in your application using reflection like:

public String getSystemProperty(String key) {
    String value = null;

    try {
        value = (String) Class.forName("android.os.SystemProperties")
                .getMethod("get", String.class).invoke(null, key);
    } catch (Exception e) {
      e.printStackTrace();
    }

    return value;
}

And then you can use it any where like:

getSystemProperty("someKey");

Try This

static String GetFromBuildProp(String PropKey) {
    Process p;
    String propvalue = "";
    try {
        p = new ProcessBuilder("/system/bin/getprop", PropKey).redirectErrorStream(true).start();
        BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));
        String line;
        while ((line = br.readLine()) != null) {
            propvalue = line;
        }
        p.destroy();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return propvalue;
}

Such as: SystemProperties.get("ro.rksdk.version")

use android.os.Build class, see http://developer.android.com/reference/android/os/Build.html, but you can not edit it without root access.

I have checked multiple devices including some Samsung and LG devices as well as a Nexus 4, latest one was the Nvidia Shield Tablet with Android 6.0. On all devices ll on /system/build.prop gave me this result(of course with varying size and date of build.prop):

-rw-r--r-- root root 3069 2015-10-13 21:48 build.prop

This means that anyone and any app without any permissions can read the file. Root would only be required for writing the non "ro."-values. You could just create a new BufferedReader(new FileReader("/system/build.prop")) and read all lines.

Advantages of this approach:

• no need for reflection (SystemProperties.get)
• no need to spawn a Process and executing getprop

Disadvantages:

• does not contain all system properties (some values e.g. are set at boot only available at runtime)
• not handy for getting a specific value compared to SystemProperties.get

On the setting page of your file manager, set home as /system, then you could browse system folders and copy build.prop and paste to sdcard. I'm still trying to root my phone but I have no problem tweaking on the way (no pun).

To read properties using reflection on the hidden API :

static public String getprop(String key){
    try { Class c = Class.forName("android.os.SystemProperties");
        try { Method method = c.getDeclaredMethod("get", String.class);
            try { return (String) method.invoke(null, key);
            }  catch (IllegalAccessException e) {e.printStackTrace();}
            catch (InvocationTargetException e) {e.printStackTrace();}
        } catch (NoSuchMethodException e) {e.printStackTrace();}
    } catch (ClassNotFoundException e) {e.printStackTrace();}
    return null;
}

To edit them (Root required) manually, you should extract them with adb :

adb pull /system/build.prop

Edit them on the computer, then "install" the new build.prop :

adb push build.prop /sdcard/
adb shell
    mount -o rw,remount -t rootfs /system
    cp /sdcard/build.prop /system/
    chmod 644 /system/build.prop

Would be safer to keep an original build.prop copy.