ic_arrow_back_white.xml

<vector xmlns:android="http://schemas.android.com/apk/res/android"
        android:width="24dp"
        android:height="24dp"
        android:viewportWidth="24.0"
        android:viewportHeight="24.0">
    <path
        android:fillColor="#FFFFFFFF"
        android:pathData="M20,11H7.83l5.59,-5.59L12,4l-8,8 8,8 1.41,-1.41L7.83,13H20v-2z"/>
</vector>

Toolbar.java

    private void setupToolbar() {
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        ActionBar ab = getSupportActionBar();
        if (ab != null) {
            ab.setDisplayHomeAsUpEnabled(true);
            ab.setHomeAsUpIndicator(R.drawable.ic_arrow_back_white);
            ab.setTitle("");
        }
    }
    
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                onBackPressed();
                break;
        }
        return true;
    }