{"id":382171,"date":"2024-08-31T20:42:49","date_gmt":"2024-08-31T13:42:49","guid":{"rendered":"https:\/\/hoanghamobile.com\/tin-tuc\/?p=382171"},"modified":"2024-08-31T20:42:49","modified_gmt":"2024-08-31T13:42:49","slug":"null-la-gi","status":"publish","type":"post","link":"https:\/\/hoanghamobile.com\/tin-tuc\/null-la-gi\/","title":{"rendered":"T\u00ecm hi\u1ec3u thu\u1eadt ng\u1eef Null l\u00e0 g\u00ec? Null trong Java ngh\u0129a l\u00e0 g\u00ec?"},"content":{"rendered":"

Ch\u1eafc h\u1eb3n b\u1ea1n \u0111\u00e3 t\u1eebng b\u1eaft g\u1eb7p v\u00f4 s\u1ed1 t\u1eeb ng\u1eef th\u00fa v\u1ecb trong ti\u1ebfng Anh. M\u1ed9t trong s\u1ed1 \u0111\u00f3 ch\u00ednh l\u00e0 Null – m\u1ed9t t\u1eeb ng\u1eef quen thu\u1ed9c trong nhi\u1ec1u l\u0129nh v\u1ef1c v\u1edbi \u00fd ngh\u0129a \u0111a d\u1ea1ng. V\u1eady “Null” l\u00e0 g\u00ec? Th\u00f4ng qua b\u00e0i vi\u1ebft d\u01b0\u1edbi \u0111\u00e2y, Ho\u00e0ng H\u00e0 Mobile s\u1ebd gi\u00fap b\u1ea1n gi\u1ea3i \u0111\u00e1p thu\u1eadt ng\u1eef n\u00e0y l\u00e0 g\u00ec v\u00e0 \u00fd ngh\u0129a c\u1ee7a t\u1eeb n\u00e0y trong Java nh\u01b0 th\u1ebf n\u00e0o nh\u00e9. B\u00e0i vi\u1ebft n\u00e0y s\u1ebd gi\u1ea3i \u0111\u00e1p m\u1ecdi th\u1eafc m\u1eafc c\u1ee7a b\u1ea1n v\u1ec1 t\u1eeb ng\u1eef th\u00fa v\u1ecb\u00a0<\/span><\/p>\n

Null l\u00e0 g\u00ec?\u00a0<\/span><\/h2>\n

Trong th\u1ebf gi\u1edbi tin h\u1ecdc, thu\u1eadt ng\u1eef Null mang m\u1ed9t \u00fd ngh\u0129a \u0111\u1eb7c bi\u1ec7t d\u00f9ng \u0111\u1ec3 bi\u1ec3u th\u1ecb s\u1ef1 v\u1eafng m\u1eb7t c\u1ee7a m\u1ed9t gi\u00e1 tr\u1ecb. Kh\u00f4ng gi\u1ed1ng nh\u01b0 s\u1ed1 0 hay m\u1ed9t chu\u1ed7i r\u1ed7ng, Null kh\u00f4ng \u0111\u1ea1i di\u1ec7n cho b\u1ea5t k\u1ef3 d\u1eef li\u1ec7u c\u1ee5 th\u1ec3 n\u00e0o. H\u00e3y t\u01b0\u1edfng t\u01b0\u1ee3ng m\u1ed9t b\u1ea3ng c\u00e2u h\u1ecfi, n\u01a1i m\u1ed9t s\u1ed1 ng\u01b0\u1eddi b\u1ecf tr\u1ed1ng m\u1ed9t c\u00e2u tr\u1ea3 l\u1eddi. \u00d4 tr\u1ed1ng \u0111\u00f3 ch\u00ednh l\u00e0 t\u01b0\u01a1ng \u0111\u01b0\u01a1ng v\u1edbi Null trong c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/span><\/p>\n

Null c\u00f3 th\u1ec3 xu\u1ea5t hi\u1ec7n trong nhi\u1ec1u ng\u1eef c\u1ea3nh kh\u00e1c nhau. Trong c\u00e1c b\u1ea3ng d\u1eef li\u1ec7u, Null c\u00f3 th\u1ec3 l\u1ea5p \u0111\u1ea7y nh\u1eefng \u00f4 c\u00f2n thi\u1ebfu th\u00f4ng tin. Trong l\u1eadp tr\u00ecnh, Null c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c g\u00e1n cho m\u1ed9t bi\u1ebfn \u0111\u1ec3 ch\u1ec9 ra r\u1eb1ng bi\u1ebfn \u0111\u00f3 ch\u01b0a ch\u1ee9a b\u1ea5t k\u1ef3 gi\u00e1 tr\u1ecb n\u00e0o. Th\u1eadm ch\u00ed trong c\u00e1c ph\u00e9p t\u00ednh to\u00e1n, Null c\u00f3 th\u1ec3 l\u00e0 k\u1ebft qu\u1ea3 khi m\u1ed9t to\u00e1n h\u1ea1ng kh\u00f4ng x\u00e1c \u0111\u1ecbnh ho\u1eb7c m\u1ed9t ph\u00e9p to\u00e1n kh\u00f4ng h\u1ee3p l\u1ec7.<\/span><\/p>\n

\"null-la-gi-1\"<\/p>\n

M\u1eb7c d\u00f9 Null c\u00f3 v\u1ebb \u0111\u01a1n gi\u1ea3n, n\u00f3 l\u1ea1i mang \u0111\u1ebfn nh\u1eefng th\u00e1ch th\u1ee9c nh\u1ea5t \u0111\u1ecbnh. Khi th\u1ef1c hi\u1ec7n c\u00e1c ph\u00e9p so s\u00e1nh ho\u1eb7c t\u00ednh to\u00e1n li\u00ean quan \u0111\u1ebfn Null, k\u1ebft qu\u1ea3 th\u01b0\u1eddng kh\u00f4ng r\u00f5 r\u00e0ng. V\u00ed d\u1ee5, 5 + Null s\u1ebd tr\u1ea3 v\u1ec1 Null, b\u1edfi v\u00ec kh\u00f4ng th\u1ec3 x\u00e1c \u0111\u1ecbnh t\u1ed5ng c\u1ee7a m\u1ed9t s\u1ed1 v\u1edbi m\u1ed9t gi\u00e1 tr\u1ecb kh\u00f4ng x\u00e1c \u0111\u1ecbnh. Do \u0111\u00f3, c\u00e1c l\u1eadp tr\u00ecnh vi\u00ean c\u1ea7n c\u1ea9n th\u1eadn x\u1eed l\u00fd Null \u0111\u1ec3 tr\u00e1nh c\u00e1c l\u1ed7i logic v\u00e0 \u0111\u1ea3m b\u1ea3o t\u00ednh ch\u00ednh x\u00e1c c\u1ee7a ch\u01b0\u01a1ng tr\u00ecnh.<\/span><\/p>\n

V\u1eady Null l\u00e0 g\u00ec? Null l\u00e0 m\u1ed9t kh\u00e1i ni\u1ec7m quan tr\u1ecdng trong tin h\u1ecdc, \u0111\u1ea1i di\u1ec7n cho s\u1ef1 thi\u1ebfu v\u1eafng th\u00f4ng tin. Hi\u1ec3u r\u00f5 v\u1ec1 Null v\u00e0 c\u00e1ch x\u1eed l\u00fd n\u00f3 l\u00e0 ch\u00eca kh\u00f3a \u0111\u1ec3 x\u00e2y d\u1ef1ng c\u00e1c \u1ee9ng d\u1ee5ng \u0111\u00e1ng tin c\u1eady v\u00e0 hi\u1ec7u qu\u1ea3.<\/span><\/p>\n

Trong Java Null l\u00e0 g\u00ec?\u00a0<\/span><\/h2>\n

Trong Java, Null l\u00e0 m\u1ed9t t\u1eeb kh\u00f3a \u0111\u1eb7c bi\u1ec7t bi\u1ec3u th\u1ecb s\u1ef1 v\u1eafng m\u1eb7t c\u1ee7a m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng. N\u00f3i c\u00e1ch kh\u00e1c, m\u1ed9t bi\u1ebfn tham chi\u1ebfu c\u00f3 gi\u00e1 tr\u1ecb Null kh\u00f4ng tr\u1ecf \u0111\u1ebfn b\u1ea5t k\u1ef3 \u0111\u1ed1i t\u01b0\u1ee3ng n\u00e0o trong b\u1ed9 nh\u1edb.<\/span><\/p>\n

Null \u0111\u00f3ng vai tr\u00f2 quan tr\u1ecdng trong vi\u1ec7c x\u1eed l\u00fd c\u00e1c t\u00ecnh hu\u1ed1ng kh\u00f4ng ch\u1eafc ch\u1eafn ho\u1eb7c kh\u00f4ng mong mu\u1ed1n trong ch\u01b0\u01a1ng tr\u00ecnh. V\u00ed d\u1ee5, m\u1ed9t ph\u01b0\u01a1ng th\u1ee9c c\u00f3 th\u1ec3 tr\u1ea3 v\u1ec1 Null n\u1ebfu kh\u00f4ng t\u00ecm th\u1ea5y k\u1ebft qu\u1ea3 ph\u00f9 h\u1ee3p, ho\u1eb7c m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng c\u00f3 th\u1ec3 c\u00f3 m\u1ed9t thu\u1ed9c t\u00ednh l\u00e0 Null n\u1ebfu ch\u01b0a \u0111\u01b0\u1ee3c kh\u1edfi t\u1ea1o.<\/span><\/p>\n

Tuy nhi\u00ean, Null c\u0169ng l\u00e0 nguy\u00ean nh\u00e2n ph\u1ed5 bi\u1ebfn g\u00e2y ra l\u1ed7i “NullPointerException”, x\u1ea3y ra khi ch\u01b0\u01a1ng tr\u00ecnh c\u1ed1 g\u1eafng truy c\u1eadp m\u1ed9t th\u00e0nh vi\u00ean (ph\u01b0\u01a1ng th\u1ee9c ho\u1eb7c thu\u1ed9c t\u00ednh) c\u1ee7a m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng Null. \u0110\u1ec3 tr\u00e1nh l\u1ed7i n\u00e0y, c\u00e1c l\u1eadp tr\u00ecnh vi\u00ean c\u1ea7n ki\u1ec3m tra c\u1ea9n th\u1eadn gi\u00e1 tr\u1ecb c\u1ee7a c\u00e1c bi\u1ebfn tham chi\u1ebfu tr\u01b0\u1edbc khi s\u1eed d\u1ee5ng ch\u00fang.<\/span><\/p>\n

\"null-la-gi-2\"<\/p>\n

Java 8 gi\u1edbi thi\u1ec7u l\u1edbp Optional nh\u01b0 m\u1ed9t c\u00e1ch an to\u00e0n h\u01a1n \u0111\u1ec3 l\u00e0m vi\u1ec7c v\u1edbi c\u00e1c gi\u00e1 tr\u1ecb c\u00f3 th\u1ec3 Null. Optional \u0111\u00f3ng g\u00f3i m\u1ed9t gi\u00e1 tr\u1ecb c\u00f3 th\u1ec3 Null v\u00e0 cung c\u1ea5p c\u00e1c ph\u01b0\u01a1ng th\u1ee9c \u0111\u1ec3 ki\u1ec3m tra s\u1ef1 t\u1ed3n t\u1ea1i c\u1ee7a gi\u00e1 tr\u1ecb, l\u1ea5y gi\u00e1 tr\u1ecb m\u1ed9t c\u00e1ch an to\u00e0n, ho\u1eb7c cung c\u1ea5p gi\u00e1 tr\u1ecb m\u1eb7c \u0111\u1ecbnh n\u1ebfu gi\u00e1 tr\u1ecb g\u1ed1c l\u00e0 Null.<\/span><\/p>\n

Null l\u00e0 m\u1ed9t kh\u00e1i ni\u1ec7m quan tr\u1ecdng trong Java, v\u1eeba h\u1eefu \u00edch trong vi\u1ec7c x\u1eed l\u00fd c\u00e1c t\u00ecnh hu\u1ed1ng kh\u00f4ng ch\u1eafc ch\u1eafn, v\u1eeba ti\u1ec1m \u1ea9n nguy c\u01a1 g\u00e2y ra l\u1ed7i. Hi\u1ec3u r\u00f5 v\u1ec1 Null v\u00e0 s\u1eed d\u1ee5ng c\u00e1c k\u1ef9 thu\u1eadt x\u1eed l\u00fd Null an to\u00e0n l\u00e0 c\u1ea7n thi\u1ebft \u0111\u1ec3 vi\u1ebft c\u00e1c ch\u01b0\u01a1ng tr\u00ecnh Java m\u1ea1nh m\u1ebd v\u00e0 \u0111\u00e1ng tin c\u1eady.<\/span><\/p>\n

Nh\u1eefng s\u1ef1 th\u1eadt v\u1ec1 Null l\u00e0 g\u00ec?\u00a0<\/span><\/h2>\n

Null, m\u1ed9t kh\u00e1i ni\u1ec7m quen thu\u1ed9c trong Java, \u0111\u00f4i khi v\u1eabn \u1ea9n ch\u1ee9a nh\u1eefng \u0111i\u1ec1u th\u00fa v\u1ecb m\u00e0 kh\u00f4ng ph\u1ea3i l\u1eadp tr\u00ecnh vi\u00ean n\u00e0o c\u0169ng bi\u1ebft. \u0110\u1ea7u ti\u00ean, Null kh\u00f4ng ph\u1ea3i l\u00e0 m\u1ed9t ki\u1ec3u d\u1eef li\u1ec7u, m\u00e0 l\u00e0 m\u1ed9t gi\u00e1 tr\u1ecb \u0111\u1eb7c bi\u1ec7t c\u00f3 th\u1ec3 g\u00e1n cho b\u1ea5t k\u1ef3 bi\u1ebfn tham chi\u1ebfu n\u00e0o, bi\u1ec3u th\u1ecb r\u1eb1ng bi\u1ebfn \u0111\u00f3 kh\u00f4ng tr\u1ecf \u0111\u1ebfn b\u1ea5t k\u1ef3 \u0111\u1ed1i t\u01b0\u1ee3ng n\u00e0o trong b\u1ed9 nh\u1edb.<\/span><\/p>\n

Th\u1ee9 hai, Null kh\u00f4ng gi\u1ed1ng nh\u01b0 chu\u1ed7i r\u1ed7ng “” hay m\u1ea3ng r\u1ed7ng []. Chu\u1ed7i r\u1ed7ng l\u00e0 m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng chu\u1ed7i c\u00f3 \u0111\u1ed9 d\u00e0i b\u1eb1ng 0, trong khi m\u1ea3ng r\u1ed7ng l\u00e0 m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng m\u1ea3ng kh\u00f4ng ch\u1ee9a ph\u1ea7n t\u1eed n\u00e0o. Ng\u01b0\u1ee3c l\u1ea1i, Null bi\u1ec3u th\u1ecb s\u1ef1 v\u1eafng m\u1eb7t ho\u00e0n to\u00e0n c\u1ee7a m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng.<\/span><\/p>\n

\"null-la-gi-3\"<\/p>\n

Th\u1ee9 ba, m\u1eb7c d\u00f9 Null c\u00f3 th\u1ec3 g\u00e1n cho m\u1ecdi bi\u1ebfn tham chi\u1ebfu, n\u00f3 l\u1ea1i kh\u00f4ng t\u01b0\u01a1ng th\u00edch v\u1edbi c\u00e1c ki\u1ec3u d\u1eef li\u1ec7u nguy\u00ean th\u1ee7y nh\u01b0 int, double, boolean,… N\u1ebfu b\u1ea1n c\u1ed1 g\u1eafng g\u00e1n Null cho m\u1ed9t bi\u1ebfn nguy\u00ean th\u1ee7y, tr\u00ecnh bi\u00ean d\u1ecbch s\u1ebd b\u00e1o l\u1ed7i. \u0110\u1ec3 bi\u1ec3u di\u1ec5n s\u1ef1 v\u1eafng m\u1eb7t c\u1ee7a gi\u00e1 tr\u1ecb trong c\u00e1c ki\u1ec3u nguy\u00ean th\u1ee7y, Java s\u1eed d\u1ee5ng c\u00e1c gi\u00e1 tr\u1ecb m\u1eb7c \u0111\u1ecbnh nh\u01b0 0 cho s\u1ed1, false cho boolean.<\/span><\/p>\n

Cu\u1ed1i c\u00f9ng, Null l\u00e0 nguy\u00ean nh\u00e2n ph\u1ed5 bi\u1ebfn g\u00e2y ra l\u1ed7i NullPointerException, m\u1ed9t ngo\u1ea1i l\u1ec7 x\u1ea3y ra khi b\u1ea1n c\u1ed1 g\u1eafng truy c\u1eadp m\u1ed9t th\u00e0nh vi\u00ean (ph\u01b0\u01a1ng th\u1ee9c ho\u1eb7c thu\u1ed9c t\u00ednh) c\u1ee7a m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng th\u00f4ng qua m\u1ed9t bi\u1ebfn tham chi\u1ebfu c\u00f3 gi\u00e1 tr\u1ecb Null. \u0110\u1ec3 tr\u00e1nh l\u1ed7i n\u00e0y, lu\u00f4n ki\u1ec3m tra gi\u00e1 tr\u1ecb c\u1ee7a bi\u1ebfn tham chi\u1ebfu tr\u01b0\u1edbc khi s\u1eed d\u1ee5ng n\u00f3.<\/span><\/p>\n

Hi\u1ec3u r\u00f5 v\u1ec1 Null v\u00e0 c\u00e1ch n\u00f3 ho\u1ea1t \u0111\u1ed9ng s\u1ebd gi\u00fap b\u1ea1n vi\u1ebft m\u00e3 Java an to\u00e0n v\u00e0 hi\u1ec7u qu\u1ea3 h\u01a1n, tr\u00e1nh \u0111\u01b0\u1ee3c nh\u1eefng l\u1ed7i kh\u00f3 ch\u1ecbu v\u00e0 n\u00e2ng cao ch\u1ea5t l\u01b0\u1ee3ng \u1ee9ng d\u1ee5ng c\u1ee7a m\u00ecnh.<\/span><\/p>\n

V\u00ec sao n\u00ean s\u1eed d\u1ee5ng Null trong ng\u00f4n ng\u1eef l\u1eadp tr\u00ecnh?\u00a0<\/span><\/h2>\n

Nh\u01b0 v\u1eady, b\u1ea1n c\u0169ng \u0111\u00e3 n\u1eafm \u0111\u01b0\u1ee3c kh\u00e1i ni\u1ec7m Null l\u00e0 g\u00ec trong Java. Null, m\u1eb7c d\u00f9 \u0111\u00f4i khi b\u1ecb xem l\u00e0 m\u1ed9t kh\u00e1i ni\u1ec7m g\u00e2y tranh c\u00e3i trong l\u1eadp tr\u00ecnh, th\u1ef1c s\u1ef1 \u0111\u00f3ng m\u1ed9t vai tr\u00f2 quan tr\u1ecdng trong vi\u1ec7c th\u1ec3 hi\u1ec7n s\u1ef1 v\u1eafng m\u1eb7t c\u1ee7a gi\u00e1 tr\u1ecb ho\u1eb7c tr\u1ea1ng th\u00e1i kh\u00f4ng x\u00e1c \u0111\u1ecbnh. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 m\u1ed9t s\u1ed1 l\u00fd do ch\u00ednh t\u1ea1i sao ch\u00fang ta n\u00ean s\u1eed d\u1ee5ng Null.\u00a0<\/span><\/p>\n

Bi\u1ec3u di\u1ec5n s\u1ef1 thi\u1ebfu th\u00f4ng tin<\/span><\/h3>\n

Trong nhi\u1ec1u t\u00ecnh hu\u1ed1ng th\u1ef1c t\u1ebf, d\u1eef li\u1ec7u c\u00f3 th\u1ec3 kh\u00f4ng t\u1ed3n t\u1ea1i ho\u1eb7c ch\u01b0a \u0111\u01b0\u1ee3c bi\u1ebft \u0111\u1ebfn t\u1ea1i m\u1ed9t th\u1eddi \u0111i\u1ec3m nh\u1ea5t \u0111\u1ecbnh. Null cung c\u1ea5p m\u1ed9t c\u00e1ch r\u00f5 r\u00e0ng \u0111\u1ec3 bi\u1ec3u th\u1ecb s\u1ef1 thi\u1ebfu th\u00f4ng tin n\u00e0y, thay v\u00ec ph\u1ea3i s\u1eed d\u1ee5ng c\u00e1c gi\u00e1 tr\u1ecb gi\u1ea3 \u0111\u1ecbnh ho\u1eb7c g\u00e2y hi\u1ec3u nh\u1ea7m. V\u00ed d\u1ee5, m\u1ed9t tr\u01b0\u1eddng “Ng\u00e0y sinh” c\u00f3 th\u1ec3 l\u00e0 Null n\u1ebfu th\u00f4ng tin n\u00e0y ch\u01b0a \u0111\u01b0\u1ee3c cung c\u1ea5p cho h\u1ec7 th\u1ed1ng.<\/span><\/p>\n

\"null-la-gi-4\"<\/p>\n

X\u1eed l\u00fd c\u00e1c tr\u01b0\u1eddng h\u1ee3p ngo\u1ea1i l\u1ec7<\/span><\/h3>\n

Trong qu\u00e1 tr\u00ecnh th\u1ef1c thi ch\u01b0\u01a1ng tr\u00ecnh, c\u00e1c l\u1ed7i ho\u1eb7c t\u00ecnh hu\u1ed1ng b\u1ea5t ng\u1edd c\u00f3 th\u1ec3 x\u1ea3y ra, d\u1eabn \u0111\u1ebfn vi\u1ec7c m\u1ed9t bi\u1ebfn ho\u1eb7c \u0111\u1ed1i t\u01b0\u1ee3ng kh\u00f4ng th\u1ec3 \u0111\u01b0\u1ee3c kh\u1edfi t\u1ea1o ho\u1eb7c g\u00e1n gi\u00e1 tr\u1ecb m\u1ed9t c\u00e1ch h\u1ee3p l\u1ec7. Null c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 bi\u1ec3u th\u1ecb tr\u1ea1ng th\u00e1i kh\u00f4ng h\u1ee3p l\u1ec7 n\u00e0y, cho ph\u00e9p ch\u01b0\u01a1ng tr\u00ecnh ph\u00e1t hi\u1ec7n v\u00e0 x\u1eed l\u00fd c\u00e1c tr\u01b0\u1eddng h\u1ee3p ngo\u1ea1i l\u1ec7 m\u1ed9t c\u00e1ch an to\u00e0n, tr\u00e1nh c\u00e1c s\u1ef1 c\u1ed1 nghi\u00eam tr\u1ecdng nh\u01b0 l\u1ed7i “NullPointerException”.<\/span><\/p>\n

\u0110\u01a1n gi\u1ea3n h\u00f3a logic ch\u01b0\u01a1ng tr\u00ecnh<\/span><\/h3>\n

Null l\u00e0 g\u00ec? Trong m\u1ed9t s\u1ed1 tr\u01b0\u1eddng h\u1ee3p, vi\u1ec7c s\u1eed d\u1ee5ng Null c\u00f3 th\u1ec3 gi\u00fap \u0111\u01a1n gi\u1ea3n h\u00f3a logic ch\u01b0\u01a1ng tr\u00ecnh, \u0111\u1eb7c bi\u1ec7t l\u00e0 khi l\u00e0m vi\u1ec7c v\u1edbi c\u00e1c c\u1ea5u tr\u00fac d\u1eef li\u1ec7u ph\u1ee9c t\u1ea1p ho\u1eb7c c\u00e1c thu\u1eadt to\u00e1n \u0111\u1ec7 quy. Null c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng nh\u01b0 m\u1ed9t \u0111i\u1ec3m d\u1eebng ho\u1eb7c \u0111i\u1ec1u ki\u1ec7n k\u1ebft th\u00fac, gi\u00fap ch\u01b0\u01a1ng tr\u00ecnh tr\u00e1nh c\u00e1c v\u00f2ng l\u1eb7p v\u00f4 h\u1ea1n ho\u1eb7c c\u00e1c tr\u01b0\u1eddng h\u1ee3p \u0111\u1eb7c bi\u1ec7t ph\u1ee9c t\u1ea1p.<\/span><\/p>\n

T\u01b0\u01a1ng th\u00edch v\u1edbi c\u00e1c h\u1ec7 th\u1ed1ng b\u00ean ngo\u00e0i<\/span><\/h3>\n

Nhi\u1ec1u h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 c\u00e1c giao th\u1ee9c trao \u0111\u1ed5i d\u1eef li\u1ec7u s\u1eed d\u1ee5ng Null \u0111\u1ec3 bi\u1ec3u di\u1ec5n c\u00e1c gi\u00e1 tr\u1ecb thi\u1ebfu ho\u1eb7c kh\u00f4ng x\u00e1c \u0111\u1ecbnh. Vi\u1ec7c s\u1eed d\u1ee5ng Null trong c\u00e1c \u1ee9ng d\u1ee5ng ph\u1ea7n m\u1ec1m gi\u00fap \u0111\u1ea3m b\u1ea3o t\u00ednh t\u01b0\u01a1ng th\u00edch v\u00e0 kh\u1ea3 n\u0103ng trao \u0111\u1ed5i d\u1eef li\u1ec7u v\u1edbi c\u00e1c h\u1ec7 th\u1ed1ng b\u00ean ngo\u00e0i n\u00e0y.<\/span><\/p>\n

\"null-la-gi-5\"<\/p>\n

Tuy nhi\u00ean, vi\u1ec7c s\u1eed d\u1ee5ng Null c\u0169ng c\u1ea7n \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n m\u1ed9t c\u00e1ch c\u1ea9n th\u1eadn v\u00e0 c\u00f3 ki\u1ec3m so\u00e1t. Vi\u1ec7c ki\u1ec3m tra Null tr\u01b0\u1edbc khi truy c\u1eadp c\u00e1c thu\u1ed9c t\u00ednh ho\u1eb7c ph\u01b0\u01a1ng th\u1ee9c c\u1ee7a m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng l\u00e0 r\u1ea5t quan tr\u1ecdng \u0111\u1ec3 tr\u00e1nh c\u00e1c l\u1ed7i NullPointerException. Ngo\u00e0i ra, vi\u1ec7c s\u1eed d\u1ee5ng c\u00e1c k\u1ef9 thu\u1eadt l\u1eadp tr\u00ecnh ph\u00f2ng th\u1ee7 v\u00e0 c\u00e1c c\u00f4ng c\u1ee5 ki\u1ec3m tra m\u00e3 ngu\u1ed3n c\u00f3 th\u1ec3 gi\u00fap ph\u00e1t hi\u1ec7n v\u00e0 ng\u0103n ng\u1eeba c\u00e1c v\u1ea5n \u0111\u1ec1 li\u00ean quan \u0111\u1ebfn Null m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3.<\/span><\/p>\n

\u0110i\u1ec3m m\u1ea1nh v\u00e0 \u0111i\u1ec3m h\u1ea1n ch\u1ebf c\u1ee7a Null l\u00e0 g\u00ec?\u00a0<\/span><\/h2>\n

Null l\u00e0 m\u1ed9t gi\u00e1 tr\u1ecb \u0111\u1eb7c bi\u1ec7t th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong l\u1eadp tr\u00ecnh \u0111\u1ec3 bi\u1ec3u th\u1ecb s\u1ef1 thi\u1ebfu v\u1eafng d\u1eef li\u1ec7u ho\u1eb7c m\u1ed9t \u0111\u1ed1i t\u01b0\u1ee3ng kh\u00f4ng t\u1ed3n t\u1ea1i. M\u1eb7c d\u00f9 c\u00f3 v\u1ebb \u0111\u01a1n gi\u1ea3n, Null mang l\u1ea1i c\u1ea3 l\u1ee3i \u00edch v\u00e0 th\u00e1ch th\u1ee9c trong qu\u00e1 tr\u00ecnh ph\u00e1t tri\u1ec3n ph\u1ea7n m\u1ec1m.<\/span><\/p>\n

\u0110i\u1ec3m m\u1ea1nh c\u1ee7a Null l\u00e0 g\u00ec?\u00a0<\/span><\/h3>\n

D\u01b0\u1edbi \u0111\u00e2y l\u00e0 m\u1ed9t s\u1ed1 \u0111i\u1ec3m h\u1ea1n ch\u1ebf c\u1ee7a Null trong Java m\u00e0 b\u1ea1n c\u00f3 th\u1ec3 tham kh\u1ea3o nh\u01b0:\u00a0<\/span><\/p>\n