how does eclipse optimize your android code

according to android reference(http://androidappdocs.appspot.com/reference/android/util/Config.html), we know that

boolean DEBUG. If this is a debug build, this field will be true.

boolean LOGD. This constant is deprecated. Always true.

boolean LOGV. This constant is deprecated. Always false.

 

I wrote hello.java in eclipse and use android SDK to build.

        setContentView(R.layout.main);

        if (Config.DEBUG) {

            Log.d("================", "Config.DEBUG=" + Config.DEBUG);

        }

        if (Config.LOGD) {

            Log.d("================", "Config.LOGD=" + Config.LOGD);

        }

        if (Config.LOGV) {

            Log.d("================", "Config.LOGV=" + Config.LOGV);

        }

        if (false) {

            Log.d("================", "false");

        }

        if (true) {

            Log.d("================", "true");

        }

by decompile hello.class, we can see how does it optimize the code during build.

1, if the value is false at build time, the code will be omit, such as Config.LOGV.

2, if the value is true at build time, the conditional judgement will be omit, such as Config.LOGD.

3, if the value is unknown at build time, the conditional judgement will not be omit. it will read the value at run time, such as Config.DEBUG.

//setContentView(R.layout.main);

     8  invokevirtual hello.world.hello.setContentView(int) : void [19]

//Log.d("================", "Config.DEBUG=" + Config.DEBUG);

    11  getstatic android.util.Config.DEBUG : boolean [23]

    14  ifeq 41

    17  ldc <String "================"> [29]

    19  new java.lang.StringBuilder [31]

    22  dup

    23  ldc <String "Config.DEBUG="> [33]

    25  invokespecial java.lang.StringBuilder(java.lang.String) [35]

    28  getstatic android.util.Config.DEBUG : boolean [23]

    31  invokevirtual java.lang.StringBuilder.append(boolean) : java.lang.StringBuilder [38]

    34  invokevirtual java.lang.StringBuilder.toString() : java.lang.String [42]

    37  invokestatic android.util.Log.d(java.lang.String, java.lang.String) : int [46]

    40  pop

//Log.d("================", "Config.LOGD=" + Config.LOGD);

    41  ldc <String "================"> [29]

    43  ldc <String "Config.LOGD=true"> [52]

    45  invokestatic android.util.Log.d(java.lang.String, java.lang.String) : int [46]

    48  pop

//Log.d("================", "true");

    49  ldc <String "================"> [29]

    51  ldc <String "true"> [54]

    53  invokestatic android.util.Log.d(java.lang.String, java.lang.String) : int [46]

    56  pop

conclusion:

1, eclipse can do necessary optimize at build time.

2, value of Config.DEBUG in android SDK is uncertain at build time.

question:

android SDK is a debug build or release build?