精选30道Java笔试题解答

package test;/** * @description Java中没有引用传递只有值传递 * * @author Alexia * @date 2013-10-16 * */class Person {private String name;private String sex;public Person(String x, String y) {this.name = x;this.sex = y;}// 重写toString()方法，方便输出public String toString() {return name + " " + sex;}// 交换对象引用public static void swapObject(Person p1, Person p2) {Person tmp = p1;p1 = p2;p2 = tmp;}// 交换基本类型public static void swapInt(int a, int b) {int tmp = a;a = b;b = tmp;}// 交换对象数组public static void swapObjectArray(Person[] p1, Person[] p2) {Person[] tmp = p1;p1 = p2;p2 = tmp;}// 交换基本类型数组public static void swapIntArray(int[] x, int[] y) {int[] tmp = x;x = y;y = tmp;}// 改变对象数组中的内容public static void changeObjectArray(Person[] p1, Person[] p2) {Person tmp = p1[1];p1[1] = p2[1];p2[1] = tmp;// 再将p1[1]修改Person p = new Person("wjl", "male");p1[1] = p;}// 改变基本类型数组中的内容public static void changeIntArray(int[] x, int[] y) {int tmp = x[1];x[1] = y[1];y[1] = tmp;x[1] = 5;}}public class ByValueTest {public static void main(String[] args) {// 建立并构造两个对象Person p1 = new Person("Alexia", "female");Person p2 = new Person("Edward", "male");System.out.println("对象交换前：p1 = " + p1.toString());System.out.println("对象交换前：p2 = " + p2.toString());// 交换p1对象和p2对象Person.swapObject(p1, p2);// 从交换结果中看出，，实际对象并未交换System.out.println("\n对象交换后：p1 = " + p1.toString());System.out.println("对象交换后：p2 = " + p2.toString());// 建立两个对象数组Person[] arraya = new Person[2];Person[] arrayb = new Person[2];// 分别构造数组对象arraya[0] = new Person("Alexia", "female");arraya[1] = new Person("Edward", "male");arrayb[0] = new Person("jmwang", "female");arrayb[1] = new Person("hwu", "male");System.out.println(‘\n’ + "对象数组交换前：arraya[0] = "+ arraya[0].toString() + ", arraya[1] = "+ arraya[1].toString());System.out.println("对象数组交换前：arrayb[0] = "+ arrayb[0].toString() + ", arrayb[1] = "+ arrayb[1].toString());// 交换这两个对象数组Person.swapObjectArray(arraya, arrayb);System.out.println(‘\n’ + "对象数组交换后：arraya[0] = "+ arraya[0].toString() + ", arraya[1] = "+ arraya[1].toString());System.out.println("对象数组交换后：arrayb[0] = "+ arrayb[0].toString() + ", arrayb[1] = "+ arrayb[1].toString());// 建立两个普通数组int[] a = new int[2];int[] b = new int[2];// 给数组个元素赋值for (int i = 0; i < a.length; i++) {a[i] = i;b[i] = i + 1;}System.out.println(‘\n’ + "基本类型数组交换前：a[0] = " + a[0] + ", a[1] = " + a[1]);System.out.println("基本类型数组交换前：b[0] = " + b[0] + ", b[1] = " + b[1]);// 交换两个基本类型数组Person.swapIntArray(a, b);System.out.println(‘\n’ + "基本类型数组交换后：a[0] = " + a[0] + ", a[1] = " + a[1]);System.out.println("基本类型数组交换后：b[0] = " + b[0] + ", b[1] = " + b[1]);// 改变对象数组的内容Person.changeObjectArray(arraya, arrayb);System.out.println(‘\n’ + "对象数组内容交换并改变后：arraya[1] = " + arraya[1].toString());System.out.println("对象数组内容交换并改变后：arrayb[1] = " + arrayb[1].toString());// 改变基本类型数组的内容Person.changeIntArray(a, b);System.out.println(‘\n’ + "基本类型数组内容交换并改变后：a[1] = " + a[1]);System.out.println("基本类型数组内容交换并改变后：b[1] = " + b[1]);}}

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