{"id":66247,"date":"2025-05-03T09:21:04","date_gmt":"2025-05-03T01:21:04","guid":{"rendered":"https:\/\/fwq.ai\/blog\/66247\/"},"modified":"2025-05-03T09:21:04","modified_gmt":"2025-05-03T01:21:04","slug":"java%e6%80%8e%e4%b9%88%e5%88%a4%e6%96%ad%e4%b8%80%e4%b8%aanull%e6%95%b0%e7%bb%84-2","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/66247\/","title":{"rendered":"java\u600e\u4e48\u5224\u65ad\u4e00\u4e2anull\u6570\u7ec4"},"content":{"rendered":"<blockquote><p>\n  \u5224\u65ad\u6570\u7ec4\u662f\u5426\u4e3a\u7a7a\u7684\u65b9\u6cd5\u6709\u4e09\u79cd\uff1a\u4f7f\u7528 == \u8fd0\u7b97\u7b26\uff1b\u4f7f\u7528 isempty() \u65b9\u6cd5\uff08\u5982\u679c\u6570\u7ec4\u662f\u7279\u5b9a\u7c7b\u578b\u7684\u6570\u7ec4\uff09\uff1b\u4f7f\u7528 length \u5c5e\u6027\uff0c\u5982\u679c length \u4e3a 0\uff0c\u5219\u6570\u7ec4\u4e3a\u7a7a\u3002\n<\/p><\/blockquote>\n<p><img decoding=\"async\" src=\"https:\/\/img.php.cn\/upload\/article\/202411\/15\/2024111504575589543.jpg\" class=\"aligncenter\" title=\"java\u600e\u4e48\u5224\u65ad\u4e00\u4e2anull\u6570\u7ec4\u63d2\u56fe\" alt=\"java\u600e\u4e48\u5224\u65ad\u4e00\u4e2anull\u6570\u7ec4\u63d2\u56fe\" \/><\/p>\n<p><strong>\u5982\u4f55\u5224\u65ad\u4e00\u4e2a\u6570\u7ec4\u662f\u5426\u662f\u7a7a\uff08null\uff09<\/strong><\/p>\n<p>\u5224\u65ad\u4e00\u4e2a\u6570\u7ec4\u662f\u5426\u662f\u7a7a\u7684\u65b9\u6cd5\u5982\u4e0b\uff1a<\/p>\n<p><strong>1. \u4f7f\u7528 == \u8fd0\u7b97\u7b26<\/strong><\/p>\n<p>\u8fd9\u662f\u6700\u7b80\u5355\u7684\u65b9\u6cd5\uff1a<\/p>\n<p><span>\u7acb\u5373\u5b66\u4e60<\/span>\u201c\u201d\uff1b<\/p>\n<pre>if (myArray == null) {\n    \/\/ \u8be5\u6570\u7ec4\u662f\u7a7a\u7684\n} else {\n    \/\/ \u8be5\u6570\u7ec4\u4e0d\u662f\u7a7a\u7684\n}<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p><strong>2. \u4f7f\u7528 isEmpty() \u65b9\u6cd5\uff08\u5982\u679c\u6570\u7ec4\u662f\u7279\u5b9a\u7c7b\u578b\u7684\u6570\u7ec4\uff09<\/strong><\/p>\n<p>\u67d0\u4e9b\u96c6\u5408\u7c7b\u63d0\u4f9b\u4e86\u4e00\u4e2a isEmpty() \u65b9\u6cd5\uff0c\u4f8b\u5982 ArrayList\uff1a<\/p>\n<pre>if (arrayList.isEmpty()) {\n    \/\/ \u8be5\u6570\u7ec4\u662f\u7a7a\u7684\n} else {\n    \/\/ \u8be5\u6570\u7ec4\u4e0d\u662f\u7a7a\u7684\n}<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p><strong>3. \u4f7f\u7528 length \u5c5e\u6027<\/strong><\/p>\n<p>\u6570\u7ec4\u7684 length \u5c5e\u6027\u8fd4\u56de\u6570\u7ec4\u4e2d\u7684\u5143\u7d20\u6570\u91cf\u3002\u5982\u679c\u8be5\u5c5e\u6027\u4e3a 0\uff0c\u5219\u6570\u7ec4\u4e3a\u7a7a\uff1a<\/p>\n<pre>if (myArray.length == 0) {\n    \/\/ \u8be5\u6570\u7ec4\u662f\u7a7a\u7684\n} else {\n    \/\/ \u8be5\u6570\u7ec4\u4e0d\u662f\u7a7a\u7684\n}<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p><strong>\u6ce8\u610f\uff1a<\/strong><\/p>\n<ul>\n<li>\u4e0d\u8981\u4f7f\u7528 != \u8fd0\u7b97\u7b26\uff0c\u56e0\u4e3a\u7a7a\u6570\u7ec4\u4e0e\u672a\u521d\u59cb\u5316\u7684\u6570\u7ec4\u4e0d\u540c\u3002<\/li>\n<li>isEmpty() \u65b9\u6cd5\u901a\u5e38\u6bd4\u5176\u4ed6\u65b9\u6cd5\u6027\u80fd\u66f4\u597d\u3002<\/li>\n<li>length \u5c5e\u6027\u5bf9\u4e8e\u57fa\u672c\u7c7b\u578b\u6570\u7ec4\u6709\u6548\uff0c\u4f46\u5bf9\u4e8e\u5f15\u7528\u7c7b\u578b\u6570\u7ec4\u65e0\u6548\u3002<\/li>\n<\/ul>\n<p>\u4ee5\u4e0a\u5c31\u662fjava\u600e\u4e48\u5224\u65ad\u4e00\u4e2anull\u6570\u7ec4\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8IDCBABY\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5224\u65ad\u6570\u7ec4\u662f\u5426\u4e3a\u7a7a\u7684\u65b9\u6cd5\u6709\u4e09\u79cd\uff1a\u4f7f\u7528 == \u8fd0\u7b97\u7b26\uff1b\u4f7f\u7528 isempty() \u65b9\u6cd5\uff08\u5982\u679c\u6570\u7ec4\u662f\u7279\u5b9a\u7c7b\u578b\u7684\u6570\u7ec4\uff09\uff1b\u4f7f\u7528 length \u5c5e\u6027\uff0c\u5982\u679c length \u4e3a 0\uff0c\u5219\u6570\u7ec4\u4e3a\u7a7a\u3002 \u5982\u4f55\u5224\u65ad\u4e00\u4e2a\u6570\u7ec4\u662f\u5426\u662f\u7a7a\uff08null\uff09 \u5224\u65ad\u4e00\u4e2a\u6570\u7ec4\u662f\u5426\u662f\u7a7a\u7684\u65b9\u6cd5\u5982\u4e0b\uff1a 1. \u4f7f\u7528 == \u8fd0\u7b97\u7b26 \u8fd9\u662f\u6700\u7b80\u5355\u7684\u65b9\u6cd5\uff1a \u7acb\u5373\u5b66\u4e60\u201c\u201d\uff1b if (myArray == null) { \/\/ \u8be5\u6570\u7ec4\u662f\u7a7a\u7684 } else { \/\/ \u8be5\u6570\u7ec4\u4e0d\u662f\u7a7a\u7684 } \u767b\u5f55\u540e\u590d\u5236 2. \u4f7f\u7528 isEmpty() \u65b9\u6cd5\uff08\u5982\u679c\u6570\u7ec4\u662f\u7279\u5b9a\u7c7b\u578b\u7684\u6570\u7ec4\uff09 \u67d0\u4e9b\u96c6\u5408\u7c7b\u63d0\u4f9b\u4e86\u4e00\u4e2a isEmpty() \u65b9\u6cd5\uff0c\u4f8b\u5982 ArrayList\uff1a if (arrayList.isEmpty()) { \/\/ \u8be5\u6570\u7ec4\u662f\u7a7a\u7684 } else { \/\/ \u8be5\u6570\u7ec4\u4e0d\u662f\u7a7a\u7684 } \u767b\u5f55\u540e\u590d\u5236 3. \u4f7f\u7528 length [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-66247","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/66247","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=66247"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/66247\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=66247"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=66247"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=66247"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}