Central Static Objects

Minecraft.getMinecraft()
    .getNetHandler()
        .getPlayerInfoMap(); // tablist
    .theWorld
        .getScoreboard(); // sidebar
        .getLoadedEntityList(); // entities - including item frames, armor stands and the wither boss used for the boss bar in the top center
        .getChunkFromBlockCoords(new BlockPos(x, y, z)); // chunk - check for example if a chunk is loaded at this position
        .getBlockState(new BlockPos(x, y, z)).getBlock(); // block - get the block in a loaded chunk
    .thePlayer
        .posX, .posY, .posZ; // player location
        .getHeldItem(); // item in hand
        .inventory; // player inventory