{
  "topic": "gc-jvm",
  "type": "fill_blank",
  "schema_version": "1.0.0",
  "generated": "2026-09-02T00:00:00Z",
  "questions": [
    {
      "id": "fb-001",
      "type": "fill_blank",
      "difficulty": 2,
      "tags": [
        "jvm",
        "gc",
        "heap"
      ],
      "question": "JVM 堆内存分为两个主要代：新生代（Young Generation）和______代。",
      "explanation": "JVM 堆主要分为新生代（包含 Eden 和 Survivor 空间）和老年代。",
      "source": null,
      "related": [],
      "answer": [
        "老"
      ],
      "answer_rule": "any"
    },
    {
      "id": "fb-002",
      "type": "fill_blank",
      "difficulty": 2,
      "tags": [
        "jvm",
        "gc",
        "heap"
      ],
      "question": "Eden、Survivor 0、Survivor 1 的默认比例是 ______。",
      "explanation": "默认情况下，新生代按 8:1:1 的比例划分为 Eden、S0 和 S1。",
      "source": null,
      "related": [],
      "answer": [
        "8:1:1"
      ],
      "answer_rule": "any"
    },
    {
      "id": "fb-003",
      "type": "fill_blank",
      "difficulty": 2,
      "tags": [
        "jvm",
        "gc",
        "heap"
      ],
      "question": "新对象优先在新生代的 ______ 区分配。",
      "explanation": "新对象优先在 Eden 区分配，Eden 区满时触发 Minor GC。",
      "source": null,
      "related": [],
      "answer": [
        "Eden"
      ],
      "answer_rule": "any"
    },
    {
      "id": "fb-004",
      "type": "fill_blank",
      "difficulty": 2,
      "tags": [
        "jvm",
        "gc",
        "heap"
      ],
      "question": "对象从新生代晋升到老年代的默认年龄阈值是 ______。",
      "explanation": "经历 15 次 GC（默认）仍然存活的对象会被晋升到老年代。",
      "source": null,
      "related": [],
      "answer": [
        "15"
      ],
      "answer_rule": "any"
    },
    {
      "id": "fb-005",
      "type": "fill_blank",
      "difficulty": 2,
      "tags": [
        "jvm",
        "gc",
        "heap"
      ],
      "question": "当 Eden 区满时，会触发 ______ GC。",
      "explanation": "Minor GC（也叫 Young GC）在 Eden 区满时触发。",
      "source": null,
      "related": [],
      "answer": [
        "Minor"
      ],
      "answer_rule": "any"
    },
    {
      "id": "fb-006",
      "type": "fill_blank",
      "difficulty": 2,
      "tags": [
        "jvm",
        "gc",
        "heap"
      ],
      "question": "三色标记法中，已被扫描但子对象尚未全部处理完成的对象标记为______色。",
      "explanation": "灰色对象已被扫描，但其子对象仍需处理。",
      "source": null,
      "related": [],
      "answer": [
        "灰"
      ],
      "answer_rule": "any"
    },
    {
      "id": "fb-007",
      "type": "fill_blank",
      "difficulty": 2,
      "tags": [
        "jvm",
        "gc",
        "heap"
      ],
      "question": "三色标记法中，尚未被扫描、将被回收的对象标记为______色。",
      "explanation": "白色对象尚未被扫描，是回收的候选对象。",
      "source": null,
      "related": [],
      "answer": [
        "白"
      ],
      "answer_rule": "any"
    },
    {
      "id": "fb-008",
      "type": "fill_blank",
      "difficulty": 2,
      "tags": [
        "jvm",
        "gc",
        "heap"
      ],
      "question": "CMS 垃圾收集器使用______更新（Incremental Update）来解决并发标记期间的漏标问题。",
      "explanation": "CMS 通过写屏障（Write Barrier）使用增量更新来追踪黑色对象新增对白色对象的引用。",
      "source": null,
      "related": [],
      "answer": [
        "增量"
      ],
      "answer_rule": "any"
    },
    {
      "id": "fb-009",
      "type": "fill_blank",
      "difficulty": 2,
      "tags": [
        "jvm",
        "gc",
        "heap"
      ],
      "question": "G1 垃圾收集器使用______（Snapshot At The Beginning）来解决漏标问题。",
      "explanation": "G1 使用 SATB，在引用被覆盖前记录旧值。",
      "source": null,
      "related": [],
      "answer": [
        "SATB"
      ],
      "answer_rule": "any"
    },
    {
      "id": "fb-010",
      "type": "fill_blank",
      "difficulty": 2,
      "tags": [
        "jvm",
        "gc",
        "heap"
      ],
      "question": "CMS 的四个阶段是：初始标记 → ______标记 → 重新标记 → 并发清除。",
      "explanation": "CMS 四阶段：Initial Mark（STW）→ Concurrent Mark → Remark（STW）→ Concurrent Sweep。",
      "source": null,
      "related": [],
      "answer": [
        "并发"
      ],
      "answer_rule": "any"
    }
  ]
}