概述
作用:用于抑制編譯器産生警告資訊,即IDEA裡面的黃色代碼塊。
抑制單類型的警告:
@SuppressWarnings("unchecked")
public void add(String item) {
List items = new ArrayList();
items.add(item);
}
抑制多類型的警告:
@SuppressWarnings(value={"unchecked", "rawtypes"})
public void add(String item) {
List items = new ArrayList();
items.add(item);
}
抑制所有類型的警告:
@SuppressWarnings("all")
通過 @SuppressWarnings 的源碼可知,其注解目标為類、字段、函數、函數入參、構造函數和函數的局部變量。建議注解應聲明在最接近警告發生的位置。
抑制警告的關鍵字
關鍵字 | 用途 |
all | to suppress all warnings |
boxing | to suppress warnings relative to boxing/unboxing operations |
UnstableApiUsage | to suppress warnings x-is-marked-unstable |
cast | to suppress warnings relative to cast operations |
dep-ann | to suppress warnings relative to deprecated annotation |
deprecation | to suppress warnings relative to deprecation |
fallthrough | to suppress warnings relative to missing breaks in switch statements |
finally | to suppress warnings relative to finally block that don’t return |
hiding | to suppress warnings relative to locals that hide variable |
incomplete-switch | to suppress warnings relative to missing entries in a switch statement (enum case) |
nls | to suppress warnings relative to non-nls string literals |
null | to suppress warnings relative to null analysis |
rawtypes | to suppress warnings relative to un-specific types when using generics on class params |
restriction | to suppress warnings relative to usage of discouraged or forbidden references |
serial | to suppress warnings relative to missing serialVersionUID field for a serializable class |
static-access | to suppress warnings relative to incorrect static access |
synthetic-access | to suppress warnings relative to unoptimized access from inner classes |
unchecked | to suppress warnings relative to unchecked operations |
unqualified-field-access | to suppress warnings relative to field access unqualified |
unused | to suppress warnings relative to unused code |
Java Lint選項
-
lint的含義
用于在編譯程式的過程中,進行更細節的額外檢查。
-
javac 的标準選項和非标準選項
标準選項:是指目前版本和未來版本中都支援的選項,如 -cp 和 -d 等。
非标準選項:是指目前版本支援,但未來不一定支援的選項。通過 javac -X 檢視目前版本支援的非标準選項。
-
檢視警告資訊
預設情況下執行 javac 僅僅顯示警告的扼要資訊,也不過阻止編譯過程。若想檢視警告的詳細資訊,則需要執行
來編譯源碼。javac -Xlint:keyword
總結
- 對于泛型,一定要指定泛型類型。而不是使用raw type,即Object類型,
,再加上SuppressWarnings注解。因為假如後面如果想要從List裡面取元素出來,可能出現錯誤的将String元素轉型為Integer,造成classCastException,或者NumberFormatException;List a = new ArrayList();
- 對于無用的方法或者類,立馬删除,而不是加
,髒代碼會破壞閱讀體驗;@SuppressWarnings("unused")