练习代码（八）对象的集合（一）

你的名字 2022-08-03 00:28 142阅读 0赞

1.封装改写一下Arrays类。  
package second;

public interface Generator \{  
Object next();  
\}  
package second;

public interface BooleanGenerator \{  
boolean next();  
\}  
package second;

public interface ByteGenerator \{  
byte next();  
\}  
package second;

public interface CharGenerator \{  
char next();  
\}  
package second;

public interface DoubleGenerator \{  
double next();  
\}  
package second;

public interface FloatGenerator \{  
float next();  
\}  
package second;

public interface IntGenerator \{  
int next();  
\}  
package second;

public interface LongGenerator \{  
long next();  
\}  
package second;

public interface ShortGenerator \{  
short next();  
\}  
在Arrays2类中实现：  
package second;

import java.util.Random;

public class Arrays2 \{

//定义8种基本类型的数组遍历.  
public static String toString(boolean\[\] n) \{  
StringBuffer results = new StringBuffer(“\[“); // 此时创建了一个对象  
// String s = new String(“abc”); 此时创建了两个对象  
for (int i = 0; i < n.length; i++) \{  
results.append(n\[i\]); // 使用StringBuffer类的append()方法添加元素  
if (i < n.length - 1)  
results.append(“,”);  
\}  
results.append(“\]”);  
return results.toString(); // 将StringBuffer类转化成String类  
\}

public static String toString(byte[] n) {
        StringBuffer results = new StringBuffer("[");
        for (int i = 0; i < n.length; i++) {
            results.append(n[i]); 
            if (i < n.length - 1)
                results.append(",");
        }
        results.append("]");
        return results.toString(); 
    }
    
    public static String toString(char[] n) {
        StringBuffer results = new StringBuffer("[");
        for (int i = 0; i < n.length; i++) {
            results.append(n[i]); 
            if (i < n.length - 1)
                results.append(",");
        }
        results.append("]");
        return results.toString(); 
    }
    
    public static String toString(short[] n) {
        StringBuffer results = new StringBuffer("[");
        for (int i = 0; i < n.length; i++) {
            results.append(n[i]); 
            if (i < n.length - 1)
                results.append(",");
        }
        results.append("]");
        return results.toString(); 
    }
    
    public static String toString(int[] n) {
        StringBuffer results = new StringBuffer("[");
        for (int i = 0; i < n.length; i++) {
            results.append(n[i]); 
            if (i < n.length - 1)
                results.append(",");
        }
        results.append("]");
        return results.toString(); 
    }
    
    public static String toString(long[] n) {
        StringBuffer results = new StringBuffer("[");
        for (int i = 0; i < n.length; i++) {
            results.append(n[i]); 
            if (i < n.length - 1)
                results.append(",");
        }
        results.append("]");
        return results.toString(); 
    }
    
    public static String toString(float[] n) {
        StringBuffer results = new StringBuffer("[");
        for (int i = 0; i < n.length; i++) {
            results.append(n[i]); 
            if (i < n.length - 1)
                results.append(",");
        }
        results.append("]");
        return results.toString(); 
    }
    
    public static String toString(double[] n) {
        StringBuffer results = new StringBuffer("[");
        for (int i = 0; i < n.length; i++) {
            results.append(n[i]); 
            if (i < n.length - 1)
                results.append(",");
        }
        results.append("]");
        return results.toString(); 
    }
    
    private static Random r = new Random();

//重新定义fill()方法，使它可以不再单一赋值.

//String类型
    public static void fill(Object[] a , Generator gen ){
    
        fill(a,0,a.length,gen);
    
    }
    
    public static void fill(Object[] a, int from, int to, Generator gen){
    
        for(int i = from;i<to;i++){
            a[i] = gen.next();
        }
    
    }
    
    public static class RandStringGenerator implements Generator{
    
        private int len;
        private RandCharGenerator cg = new RandCharGenerator();
    
        public RandStringGenerator(int length){
            len = length;
        }
    
        @Override
        public Object next() {
            // TODO Auto-generated method stub
            char[] c = new char[len];
            for(int i = 0; i < len; i++)
                c[i] = cg.next();
            return new String(c);
        }
    
    }
    
    //Boolean类型
    public static void fill(boolean[] a , BooleanGenerator gen ){
    
        fill(a,0,a.length,gen);
    
    }
    
    public static void fill(boolean[] a, int from, int to, BooleanGenerator gen){
    
        for(int i = from;i<to;i++){
            a[i] = gen.next();
        }
    
    }
    
    public static class RandBooleanGenerator implements BooleanGenerator{
    
        @Override
        public boolean next() {
            // TODO Auto-generated method stub
            return r.nextBoolean();
        }
    
    }
    
    //Byte类型
    public static void fill(byte[] a , ByteGenerator gen ){
    
        fill(a,0,a.length,gen);
    
    }
    
    public static void fill(byte[] a, int from, int to, ByteGenerator gen){
    
        for(int i = from;i<to;i++){
            a[i] = gen.next();
        }
    
    }
    
    public static class RandByteGenerator implements ByteGenerator{
    
        @Override
        public byte next() {
            // TODO Auto-generated method stub
            return (byte)r.nextInt();
        }
    
    }
    
    //Char类型
    public static void fill(char[] a , CharGenerator gen ){
    
        fill(a,0,a.length,gen);
    
    }
    
    public static void fill(char[] a, int from, int to, CharGenerator gen){
    
        for(int i = from;i<to;i++){
            a[i] = gen.next();
        }
    
    }
    
    private static String ssource = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
    private static char[] src = ssource.toCharArray();
    
    public static class RandCharGenerator implements CharGenerator{
    
        @Override
        public char next() {
            // TODO Auto-generated method stub
            return src[r.nextInt(src.length)];
        }
    
    }
    
    //Short类型
    public static void fill(short[] a , ShortGenerator gen ){
    
        fill(a,0,a.length,gen);
    
    }
    
    public static void fill(short[] a, int from, int to, ShortGenerator gen){
    
        for(int i = from;i<to;i++){
            a[i] = gen.next();
        }
    
    }
    
    public static class RandShortGenerator implements ShortGenerator{
    
        @Override
        public short next() {
            // TODO Auto-generated method stub
            return (short)r.nextInt();
        }
    
    }
    
    //Int类型
    public static void fill(int[] a , IntGenerator gen ){
    
        fill(a,0,a.length,gen);
    
    }
    
    public static void fill(int[] a, int from, int to, IntGenerator gen){
    
        for(int i = from;i<to;i++){
            a[i] = gen.next();
        }
    
    }
    
    public static class RandIntGenerator implements IntGenerator{
    
        private int mod = 10000;
    
        public RandIntGenerator(){}
    
        public RandIntGenerator(int modulo){ mod = modulo; }
    
        @Override
        public int next() {
            // TODO Auto-generated method stub
            return r.nextInt(mod);
        }
    
    }
    
    //Long类型
    public static void fill(long[] a , LongGenerator gen ){
    
        fill(a,0,a.length,gen);
    
    }
    
    public static void fill(long[] a, int from, int to, LongGenerator gen){
    
        for(int i = from;i<to;i++){
            a[i] = gen.next();
        }
    
    }
    
    public static class RandLongGenerator implements LongGenerator{
    
        @Override
        public long next() {
            // TODO Auto-generated method stub
            return (long)r.nextInt();
        }
    
    }
    
    //Float类型
    public static void fill(float[] a , FloatGenerator gen ){
    
        fill(a,0,a.length,gen);
    
    }
    
    public static void fill(float[] a, int from, int to, FloatGenerator gen){
    
        for(int i = from;i<to;i++){
            a[i] = gen.next();
        }
    
    }
    
    public static class RandFloatGenerator implements FloatGenerator{
    
        @Override
        public float next() {
            // TODO Auto-generated method stub
            return (float)r.nextInt();
        }
    
    }
    
    //Doouble类型
    public static void fill(double[] a , DoubleGenerator gen ){
    
        fill(a,0,a.length,gen);
    
    }
    
    public static void fill(double[] a, int from, int to, DoubleGenerator gen){
    
        for(int i = from;i<to;i++){
            a[i] = gen.next();
        }
    
    }
    
    public static class RandDoubleGenerator implements DoubleGenerator{
    
        @Override
        public double next() {
            // TODO Auto-generated method stub
            return (double)r.nextInt();
        }
    
    }

\}  
2.测试封装的Arrays2类。  
package first;  
import java.util.Arrays;

import second.Arrays2;;

public class TestArrays2 \{

public static void main(String[] args) {
    
        int size = 6;
    
        if(args.length != 0)
            size = Integer.parseInt(args[0]);
            if(size < 3){
                System.out.println("arg must be >= 3");
                System.exit(1);
            }
    
        //定义基本类型数组
        boolean[] a1 = new boolean[size];
        byte[] a2 = new byte[size];
        char[] a3 = new char[size];
        short[] a4 = new short[size];
        int[] a5 = new int[size];
        long[] a6 = new long[size];
        float[] a7 = new float[size];
        double[] a8 = new double[size];
    
        //填充基本类型数组,并输出.
        Arrays2.fill(a1, new Arrays2.RandBooleanGenerator());
        System.out.println(Arrays2.toString(a1));
        Arrays2.fill(a2, new Arrays2.RandByteGenerator());
        System.out.println(Arrays2.toString(a2));
        Arrays2.fill(a3, new Arrays2.RandCharGenerator());
        System.out.println(Arrays2.toString(a3));
        Arrays2.fill(a4, new Arrays2.RandShortGenerator());
        System.out.println(Arrays2.toString(a4));
        Arrays2.fill(a5, new Arrays2.RandIntGenerator());
        System.out.println(Arrays2.toString(a5));
        Arrays2.fill(a6, new Arrays2.RandLongGenerator());
        System.out.println(Arrays2.toString(a6));
        Arrays2.fill(a7, new Arrays2.RandFloatGenerator());
        System.out.println(Arrays2.toString(a7));
        Arrays2.fill(a8, new Arrays2.RandDoubleGenerator());
        System.out.println(Arrays2.toString(a8));
    
        //调用Arrays类的sort()方法对数组进行排序.
    
        Arrays.sort(a5);
        System.out.println("排序后："+Arrays2.toString(a5));
    
    }

\}  
3.数组的比较。  
package first;

import java.util.Arrays;

public class CompairArrays \{

public static void main(String[] args){
    
        String[] s1 = new String[5];
        Arrays.fill(s1, "hi");
    
        String[] s2 = {"hi","hi","hi","hi","hi"};
    
        System.out.println(s1==s2);                // == 比较的是对象的引用
        System.out.println(Arrays.equals(s1,s2));  // equals 比较的是对象
    
    }

\}  
4.数组的复制。  
package first;

import java.util.Arrays;

class Arrays2 \{

public static String toString(int[] n) {
        StringBuffer results = new StringBuffer("["); //     此时创建了一个对象

// String s = new String(“abc”); 此时创建了两个对象  
for (int i = 0; i < n.length; i++) \{  
results.append(n\[i\]); // 使用StringBuffer类的append()方法添加元素  
if (i < n.length - 1)  
results.append(“,”);  
\}  
results.append(“\]”);  
return results.toString(); // 将StringBuffer类转化成String类  
\}

public class CopyingArrays \{

public static void main(String[] args) {
      // 基本类型数组
        // 定义两个数组，并用Arrays类中的fill()方法填充数组.
        int[] i = new int[7];
        int[] j = new int[10];
        Arrays.fill(i, 47);
        Arrays.fill(j, 97);
    
        // 调用Arrays2类中的toString()方法输出数组.
        System.out.println(Arrays2.toString(i));
        System.out.println(Arrays2.toString(j));
    
        // 调用Java标准类库中static System.arraycopy()方法，来复制数组.
        System.arraycopy(i, 0, j, 0, i.length);
    
        System.out.println(Arrays2.toString(j));
    
        int[] k = new int[5];
        Arrays.fill(k, 105);
        System.arraycopy(i, 0, k, 0, k.length);
        System.out.println(Arrays2.toString(k));
    
        Arrays.fill(k, 105);
        System.arraycopy(k, 0, i, 2, k.length);
        System.out.println(Arrays2.toString(i));
    
      // 对象数组
        // 调用Arrays.asList()方法将数组转化成List容器.
        Integer[] u = new Integer[10];
        Integer[] v = new Integer[5];
        Arrays.fill(u, new Integer(23));
        Arrays.fill(v, new Integer(86));
    
        System.out.println(Arrays.asList(u));
        System.out.println(Arrays.asList(v));
    
        System.arraycopy(v, 0, u, 0, v.length);
        System.out.println(Arrays.asList(u));
    
    }

\}  
5.返回一个数组并输出。  
package first;

import java.util.Random;

public class IceCream \{

public static final String[] flavors = { "a", "b", "c", "d", "e", "f", "g","h" };
    private static Random r = new Random();
    
    public static String[] flavorSet(int n) {
    
        String[] results = new String[n];
        boolean[] b = new boolean[flavors.length];
    
        for (int i = 0; i < n; i++) {
    
            int t;
    
            do
                t = r.nextInt(flavors.length);  
            while (b[t]);
    
            results[i] = flavors[t];
            b[t] = true;
        }
        return results;
    }
    
    public static void main(String[] args){
    
        for(int i = 0; i < 20; i++){
    
            System.out.println("flavorSet("+i+")=");
    
            String[] fl = flavorSet(flavors.length);
    
            for(int j = 0; j < fl.length; j++){
                System.out.println("\t"+fl[j]);
            }
        }
    }