java用递归法在数组中查找，插入

先来看原题要求

package integerSet;/** * This class provides methods to interact with a set of integers * implemented using a normal array of integers. * You <b>should</b> at least modify the * methods <code>member</code> (is an integer in the set)  * and <code>insert</code> (add a new integer to the set). * You may add new methods if you so wish. */public class IntegerSet {    // You may define new variables here if needed    /**     * Returns <code>true</code> if the array <code>setArray</code>     * contains <code>element</code>.     * <p>     * This method <strong>must</strong> be implemented using     * <em>recursion</em>. That is, you are not allowed to use     * iterators, <code>for</code> loops, <code>while</code> loops     * and similar techniques to implement member, rather you should     * call a method defined by you recursively.     * <p>     * Note that the <code>null</code>     * reference indicates that the array does not contain an element     * at that position.     */    public static boolean member(int element, Integer setArray[]) {// You SHOULD change the body of this methodreturn false;    }    /**     * Inserts the integer <code>element</code>      * in the <code>setArray</code> array argument, if it not     * already present (and if there is space to insert it).     * Integers can be inserted in array cells which contain <code>null</code>.     * <p>     * Returns <code>true</code> if the element was inserted,     * and <code>false</code> otherwise (the integer was already in     * the array, or there is no space in the array).     * <p>     * This method <strong>must</strong> be implemented <em>without</em>     * using recursion. That is, you should use a <code>for</code> loop,      * or a <code>while</code> loop to implement insert, you should     * not use recursion nor should you use iterators.     * <p>     * You <em>may</em> however call your method     * <code>member</code> to check whether the array     * already contains the element to add.     */    public static boolean insert(int element, Integer setArray[]) {// You SHOULD change the body of this methodreturn false;    }}

什么是递归？

在数学与计算机科学中，是指在函数的定义中使用函数自身的方法。如：从前有座山，山里有座庙，庙里有个老和尚，正在给小和尚讲故事呢！故事是什么呢？「从前有座山，山里有座庙，庙里有个老和尚，正在给小和尚讲故事呢！故事是什么呢？『从前有座山，山里有座庙，庙里有个老和尚，正在给小和尚讲故事呢！故事是什么呢？……』」

题中要求，用递归方法来在数组中查找元素是否存在，若存在返回true，反之则返回false。并要求在此数组中插入元素，条件为有位置，且该数组不包含与此元素相同的元素，并将是否可以插入结果返回。

贴上完整程序

public class IntegerSet {    // You may define new variables here if needed    static int i=0; public static boolean member(int element, Integer setArray[]) {// You SHOULD change the body of this method    boolean sol = false;        if(i<setArray.length){    if(setArray[i] != null && setArray[i] == element){    return true;    }    else{    i++;     sol = member(element,setArray);    }    }    i=0;//将i归0，方便下次寻找    return sol;    } public static boolean insert(int element, Integer setArray[]) {// You SHOULD change the body of this method    boolean sol = false;    boolean aux = member(element, setArray);//寻找此element是否存在于数组中    for(int i=0;i<setArray.length && !sol && !aux;i++){    if(setArray[i]==null){    setArray[i]=element;//若此位置为空，则插入element    sol=true;    }    }    return sol;    }}

附上tester

package integerSet;/** * This class provides methods to test your implementation of * the <code>IntegerSet</code> implementation. */public class Tester {    /**     * Runs the test suite.     */    public static void main(String args[]) {doTest();    }    /**     * Executes the test suite.     */    public static void doTest() {Integer s0[] = {0,1,2,3,4};if (!IntegerSet.member(3,s0)) {    System.out.println("3 should be a member of {0,1,2,3,4}");    throw new Error();}if (IntegerSet.member(7,s0)) {    System.out.println("7 should not be a member of {0,1,2,3,4}");    throw new Error();}if (IntegerSet.insert(7,s0)) {    System.out.println("it should not be possible to insert 7 in {0,1,2,3,4}");    throw new Error();}if (IntegerSet.member(7,s0)) {    System.out.println("7 should not be a member of {0,1,2,3,4}");    throw new Error();}Integer s1[] = {4,1,2,null,3};if (!IntegerSet.member(4,s1)) {    System.out.println("4 should be a member of {4,1,2,null,3}");    throw new Error();}if (!IntegerSet.member(3,s1)) {    System.out.println("3 should be a member of {4,1,2,null,3}");    throw new Error();}if (IntegerSet.member(7,s1)) {    System.out.println("7 should not be a member of {4,1,2,null,3}");    throw new Error();}if (!IntegerSet.insert(7,s1)) {    System.out.println("it should be possible to insert 7 in {4,1,2,null,3}");    throw new Error();}if (!IntegerSet.member(7,s1)) {    System.out.println("7 should be a member of {4,1,2,7,3}");    throw new Error();}if (IntegerSet.insert(7,s1)) {    System.out.println("it should not possible to insert 7 in {4,1,2,7,3}");    throw new Error();}if (!IntegerSet.member(7,s1)) {    System.out.println("7 should be a member of {4,1,2,7,3}");    throw new Error();}Integer s2[] = {};if (IntegerSet.member(1,s2)) {    System.out.println("1 should not be a member of {}");    throw new Error();}if (IntegerSet.insert(1,s2)) {    System.out.println("it should not possible to insert 1 in {}");    throw new Error();}if (IntegerSet.member(1,s2)) {    System.out.println("1 should not be a member of {}");    throw new Error();}Integer s3[] = {null};if (IntegerSet.member(-1,s3)) {    System.out.println("-1 should not be a member of {null}");    throw new Error();}if (!IntegerSet.insert(-1,s3)) {    System.out.println("it should be possible to insert -1 in {null}");    throw new Error();}if (!IntegerSet.member(-1,s3)) {    System.out.println("-1 should be a member of {-1}");    throw new Error();}System.out.println("OK!");    }}