How to detect android device is 64 bit or 32 bit processor?

 try {
            boolean  isArm64 = false;

            BufferedReader localBufferedReader = new BufferedReader(new FileReader("/proc/cpuinfo"));
            if (localBufferedReader.readLine().contains("aarch64")) {
                isArm64 = true;
            }
            localBufferedReader.close();
        } catch (IOException e) {
        }

Or

final boolean is64bit = Build.SUPPORTED_64_BIT_ABIS.length > 0;

If you're using ADB

adb shell cat /proc/cpuinfo | grep rch

Most outputs:

Architecture 7 -> 32bit

Architecture 8 -> 64bit

• this is an extension answer from @Naval Kishor Jha

• tested in 6 models here

• no root needed

If you're using JAVA

if(Build.SUPPORTED_64_BIT_ABIS.length>0)
  {
  //it's a 64bit
  }
  else
  {
  //it's a 32bit
  }

Simple answer: There's no need to check for this on Android versions below Lollipop. That's due the fact that Lollipop introducted platform support for 64-Bit architectures, Android-Versions below Lollipop won't run with a 64-Bit processor.

Android 5.0 introduces platform support for 64-bit architectures—used by the Nexus 9's NVIDIA Tegra K1. Optimizations provide larger address space and improved performance for certain compute workloads. Apps written in the Java language run as 64-bit apps automatically—no modifications are needed. If your app uses native code, we’ve extended the NDK to support new ABIs for ARM v8, and x86-64, and MIPS-64. (Source)

Firdt connect the device ato system, on windows type in the command prompt this command

adb shell cat  /proc/cpuinfo | findstr arc

on linux or mac base system open terminal and type this command

  adb shell cat  /proc/cpuinfo | grep arc

if first line of out contain 32 that mean system type is 32bit

first line of out if contain 64 that mean system type is 64bit