Java Collections is the same as c++ stl.
1 public static final String[] supportTypes = new String[]{"image/jpeg", "image/png", "image/jpg"};
isAllowExtension = Arrays.asList(supportTypes).contains("image/jpeg");
2 list element is class
List<FileSaveResult> results = new ArrayList<>();
results.add(new FileSaveResult(contentType, fileItem.getName(), file));//list put class FileSaveResult
saveResult = uploadResult.get(0);//list get class
String path =saveResult.getFile().getAbsolutePath() ; //class get file to get path value
3 Collections2.transform:同步做两件事。
1) 通过函数，将value改变。参数1 configDataList 对应参数2 ConfigData，定义input，input.getConfigKey()传入， return string
2 )将List转成Collection。 Collection is list base class.
List<ConfigData> configDataList;
Collection<String> fieldKeys =Collections2.transform(configDataList, new Function<ConfigData, String>() {
@Override
public String apply(ConfigData input) {
return ConfigVarConverter.configKeyToString(input.getConfigKey());
}
});
public static String configKeyToString(ConfigKey configKey) {
StringBuilder sbFQName = new StringBuilder(configKey.getKey().getFqName());
......
return sbFQName.toString();
}