Java は StringBuffer が空かどうかを判断します

        StringBuffer sb = new StringBuffer();
        if (sb.length() == 0 || sb.toString().trim().equals("")) {
    
    
            System.out.println("StringBuffer is empty.");
        } 
        或
        if (TextUtils.isEmpty(sb.toString())) {
    
    
			System.out.println("StringBuffer is empty.");
        }