2026年Java开发面试技巧及高频题含答案

2026年Java开发面试技巧及高频题含答案一、选择题（共10题，每题2分，合计20分）1.在Java中，以下哪个关键字用于声明一个不可变类？A.finalB.staticC.abstractD.synchronized2.Java8中，哪个方法用于获取集合中第一个元素？A.getFirst()B.first()C.get(0)D.getFirstElement()3.在Java中，以下哪个注解用于标记一个类是泛型类？A.@GenericB.@GenericClassC.@ClassGenericD.@GenericClass4.Java中，以下哪个集合类不允许存储重复元素？A.ArrayListB.LinkedListC.HashSetD.HashMap5.在Java中，以下哪个关键字用于声明一个接口？A.interfaceB.implementC.classD.abstract6.Java中，以下哪个方法用于关闭并释放资源？A.close()B.finalize()C.dispose()D.destroy()7.在Java中，以下哪个注解用于标记一个方法为测试方法？A.@TestB.@TestMethodC.@testD.@JUnitTest8.Java中，以下哪个关键字用于声明一个静态变量？A.staticB.finalC.constD.volatile9.在Java中，以下哪个类用于处理日期和时间？A.DateB.CalendarC.LocalDateTimeD.DateTime10.Java中，以下哪个方法用于判断一个字符串是否为空或空白？A.isEmpty()B.isBlank()C.isNull()D.isWhitespace()二、简答题（共5题，每题4分，合计20分）1.简述Java中的泛型是什么，并举例说明其应用场景。2.解释Java中的反射机制及其主要用途。3.简述Java中的多线程实现方式，并比较线程池与手动创建线程的优缺点。4.解释Java中的异常处理机制，并说明try-catch-finally语句的执行顺序。5.简述Spring框架的核心概念，并说明SpringBoot的主要优势。三、编程题（共5题，每题10分，合计50分）1.编写一个Java方法，实现快速排序算法，并测试其功能。javapublicclassQuickSort{publicstaticvoidquickSort(int[]arr,intlow,inthigh){if(low<high){intpivot=partition(arr,low,high);quickSort(arr,low,pivot-1);quickSort(arr,pivot+1,high);}}privatestaticintpartition(int[]arr,intlow,inthigh){intpivot=arr[high];inti=(low-1);for(intj=low;j<high;j++){if(arr[j]<pivot){i++;inttemp=arr[i];arr[i]=arr[j];arr[j]=temp;}}inttemp=arr[i+1];arr[i+1]=arr[high];arr[high]=temp;returni+1;}publicstaticvoidmain(String[]args){int[]arr={10,7,8,9,1,5};quickSort(arr,0,arr.length-1);System.out.println(Arrays.toString(arr));}}2.编写一个Java方法，实现二叉树的深度优先遍历（前序、中序、后序），并测试其功能。javaclassTreeNode{intval;TreeNodeleft;TreeNoderight;TreeNode(intx){val=x;}}classBinaryTree{TreeNoderoot;publicvoidpreOrder(TreeNodenode){if(node==null)return;System.out.print(node.val+"");preOrder(node.left);preOrder(node.right);}publicvoidinOrder(TreeNodenode){if(node==null)return;inOrder(node.left);System.out.print(node.val+"");inOrder(node.right);}publicvoidpostOrder(TreeNodenode){if(node==null)return;postOrder(node.left);postOrder(node.right);System.out.print(node.val+"");}publicstaticvoidmain(String[]args){BinaryTreetree=newBinaryTree();tree.root=newTreeNode(1);tree.root.left=newTreeNode(2);tree.root.right=newTreeNode(3);tree.root.left.left=newTreeNode(4);tree.root.left.right=newTreeNode(5);System.out.println("PreOrder:");tree.preOrder(tree.root);System.out.println("\nInOrder:");tree.inOrder(tree.root);System.out.println("\nPostOrder:");tree.postOrder(tree.root);}}3.编写一个Java方法，实现一个简单的LRU缓存机制，并测试其功能。javaimportjava.util.HashMap;importjava.util.Map;classLRUCache<K,V>{privatefinalintcapacity;privatefinalMap<K,Node<K,V>>map;privateNode<K,V>head,tail;publicLRUCache(intcapacity){this.capacity=capacity;this.map=newHashMap<>();}publicVget(Kkey){Node<K,V>node=map.get(key);if(node==null)returnnull;moveToHead(node);returnnode.value;}publicvoidput(Kkey,Vvalue){Node<K,V>node=map.get(key);if(node==null){Node<K,V>newNode=newNode<>(key,value);map.put(key,newNode);addNode(newNode);if(map.size()>capacity){Node<K,V>tail=removeTail();map.remove(tail.key);}}else{node.value=value;moveToHead(node);}}privatevoidaddNode(Node<K,V>node){node.next=head;node.prev=null;if(head!=null)head.prev=node;head=node;if(tail==null)tail=node;}privatevoidremoveNode(Node<K,V>node){if(node.prev!=null)node.prev.next=node.next;if(node.next!=null)node.next.prev=node.prev;if(node==head)head=node.next;if(node==tail)tail=node.prev;}privatevoidmoveToHead(Node<K,V>node){removeNode(node);addNode(node);}privateNode<K,V>removeTail(){Node<K,V>res=tail;removeNode(tail);returnres;}staticclassNode<K,V>{Kkey;Vvalue;Node<K,V>prev;Node<K,V>next;Node(Kkey,Vvalue){this.key=key;this.value=value;}}publicstaticvoidmain(String[]args){LRUCache<Integer,Integer>cache=newLRUCache<>(2);cache.put(1,1);cache.put(2,2);System.out.println(cache.get(1));//1cache.put(3,3);//evictskey2System.out.println(cache.get(2));//-1(notfound)cache.put(4,4);//evictskey1System.out.println(cache.get(1));//-1(notfound)System.out.println(cache.get(3));//3System.out.println(cache.get(4));//4}}4.编写一个Java方法，实现一个简单的KMP算法，并测试其功能。javapublicclassKMP{publicstaticvoidmain(String[]args){Stringtxt="ABABDABACDABABCABAB";Stringpat="ABABCABAB";KMPSearch(pat,txt);}publicstaticvoidKMPSearch(Stringpat,Stringtxt){intM=pat.length();intN=txt.length();int[]lps=newint[M];intj=0;computeLPSArray(pat,M,lps);inti=0;while(i<N){if(pat.charAt(j)==txt.charAt(i)){j++;i++;}if(j==M){System.out.println("Foundpatternatindex"+(i-j));j=lps[j-1];}elseif(i<N&&pat.charAt(j)!=txt.charAt(i)){if(j!=0){j=lps[j-1];}else{i=i+1;}}}}publicstaticvoidcomputeLPSArray(Stringpat,intM,int[]lps){intlen=0;inti=1;lps[0]=0;while(i<M){if(pat.charAt(i)==pat.charAt(len)){len++;lps[i]=len;i++;}else{if(len!=0){len=lps[len-1];}else{lps[i]=len;i++;}}}}}5.编写一个Java方法，实现一个简单的LRU缓存机制，并测试其功能。javaimportjava.util.HashMap;importjava.util.Map;classLRUCache<K,V>{privatefinalintcapacity;privatefinalMap<K,Node<K,V>>map;privateNode<K,V>head,tail;publicLRUCache(intcapacity){this.capacity=capacity;this.map=newHashMap<>();}publicVget(Kkey){Node<K,V>node=map.get(key);if(node==null)returnnull;moveToHead(node);returnnode.value;}publicvoidput(Kkey,Vvalue){Node<K,V>node=map.get(key);if(node==null){Node<K,V>newNode=newNode<>(key,value);map.put(key,newNode);addNode(newNode);if(map.size()>capacity){Node<K,V>tail=removeTail();map.remove(tail.key);}}else{node.value=value;moveToHead(node);}}privatevoidaddNode(Node<K,V>node){node.next=head;node.prev=null;if(head!=null)head.prev=node;head=node;if(tail==null)tail=node;}privatevoidremoveNode(Node<K,V>node){if(node.prev!=null)node.prev.next=node.next;if(node.next!=null)node.next.prev=node.prev;if(node==head)head=node.next;if(node==tail)tail=node.prev;}privatevoidmoveToHead(Node<K,V>node){removeNode(node);addNode(node);}priva