Java 程式設計 -- 陣列

Java 程式

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運算式

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簡體版

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範例：一維陣列

class Array1 {
  public static void main(String[] args) throws Exception {
    String[] names={"大毛","二毛","小毛"};
    String[] tels={"082-31333","082-31111","082-31222"};
    for (int i=0; i<names.length; i++)
      System.out.println(names[i]+" "+tels[i]);
  }
}

範例：循序搜尋

class People3
{ 
  public static void main(String[] args)
  {
    String target = "二毛";
    if (args.length > 0) target = args[0];
    String[] name={"大毛","二毛","小毛" };
    String[] tel={"31333","31111","31222"};
    for (int i=0; i<3; i++)
    {
      if (target.equals("") || name[i].equals(target))
        System.out.println(name[i]+ ":"+tel[i]);
    }
  }
}

向量與內積

public class Vector {
      public static void main(String[] args) {
          double x[] = {1.0, 2.0, 3.0};
          double y[] = {4.0, 5.0, 6.0};
          print(x);
          print(y);
          double z[] = new double[x.length];
          add(x, y, z);
          print(z);
 
          double xy = dot(x, y);
          System.out.println("x*y="+xy);
      }
 
      public static void print(double a[]) {
          for (int i=0; i<a.length; i++)
              System.out.print(a[i]+" ");
          System.out.println();
      }
 
      public static void add(double a[], double b[], double c[]) {
          for (int i=0; i<a.length; i++)
              c[i] = a[i] + b[i];
      }
 
      public static double dot(double a[], double b[]) {
          double result = 0.0;
          for (int i=0; i<a.length; i++)
              result += a[i]*b[i];
          return result;
      }
}

範例：二維陣列列印

class Array2 {
  public static void main(String[] args)
  {
    int a[][] = {{1,2}, {3,4}};
    System.out.println("=======a=======");
    for (int i=0; i<a.length; i++)
    {
      for (int j=0; j<a[i].length; j++)
        System.out.print(a[i][j]+" ");
      System.out.println();
    }
  }
}

範例：二維陣列加總

class Array3 
{
    public static void main(String[] args) 
    {
        int a[][] = {{1,2,3}, {4,5,6}};
        int sum = 0;
        for (int i=0; i<a.length; i++)
        {
            for (int j=0; j<a[i].length; j++)
              sum += a[i][j];
        }
        System.out.println("sum(a) = "+sum);
    }
}

範例：兩個陣列相加

class Matrix1 {
    public static void main(String[] args) {
        int A[][] = {{1,2}, {3,4}};
        int B[][] = {{5,6}, {7,8}};
        int C[][] = new int[2][2];
        for (int i=0; i<C.length; i++) {
            for (int j=0; j<C[0].length; j++) {
                int sum = 0;
                for (int k=0; k<2; k++) {
                    sum = sum+A[i][k]*B[k][j];
                }
                C[i][j] = sum;
            }
        }
        for (int i=0; i<C.length; i++) {
            for (int j=0; j<C[0].length; j++) {
                System.out.print(C[i][j]+" ");
            }
            System.out.println();
        }
    }
}

範例：兩陣列相加 (函數版)

class Array2 {
  public static void main(String[] args)
  {
    int x[][] = {{1,2}, {3,4}};
    int y[][] = {{3,4}, {7,8}};
    int z[][] = new int[2][2];
    System.out.println("========= x ==========");
    print(x);
    System.out.println("========= y ==========");
    print(y);
    add(x,y,z);
    System.out.println("========= z ==========");
    print(z);
  }
 
  public static void add(int a[][], int b[][], int c[][]) {
        for (int i=0; i<a.length; i++)
        {
          for (int j=0; j<a[i].length; j++)
              c[i][j] = a[i][j]+b[i][j];
        }
  }
 
  public static void print(int a[][]) {
        for (int i=0; i<a.length; i++)
        {
          for (int j=0; j<a[i].length; j++)
            System.out.print(a[i][j]+"\t");
          System.out.println();
        }
  }
}

範例：矩陣物件

class Matrix2 {
  public static void main(String[] args) {
    double A[][] = {{1,2}, {3,4}};
    double B[][] = {{5,6}, {7,8}};
    double C[][] = new double[2][2];
    double D[][] = new double[2][2];
    add(A, B, C);
    System.out.println("========C========");
    print(C);
    dot(A, B, D);
    System.out.println("========D========");
    print(D);
    double sum = sum(D);
    System.out.println("sum(D)="+sum);
    not(D);
    System.out.println("========not(D)========");
    print(D);
  }
 
  public static void print(double A[][]) 
  {
    for (int i=0; i<A.length; i++) 
    {
      for (int j=0; j<A[0].length; j++) 
         System.out.print(A[i][j]+" ");
      System.out.println();
    }
  }
 
  public static void not(double A[][]) 
  {
    for (int i=0; i<A.length; i++) 
      for (int j=0; j<A[0].length; j++) 
        A[i][j] = -A[i][j];
  }
 
  public static double sum(double A[][]) 
  {
    double total = 0;
    for (int i=0; i<A.length; i++) 
      for (int j=0; j<A[0].length; j++) 
        total += A[i][j];
    return total;
  }
 
  public static void add(double A[][], double B[][], double C[][]) 
  {
    for (int i=0; i<A.length; i++) 
      for (int j=0; j<A[0].length; j++) 
        C[i][j] = A[i][j] + B[i][j];
  }
 
  public static void dot(double A[][], double B[][], double C[][]) 
  {
    for (int i=0; i<C.length; i++) 
      for (int j=0; j<C[0].length; j++) 
      {
        double sum = 0;
        for (int k=0; k<2; k++) 
            sum = sum+A[i][k]*B[k][j];
        C[i][j] = sum;
      }
  }
}

範例：記憶體電話簿

import java.io.*;
import java.util.*;
 
public class TelBook 
{
    public static void main(String args[]) throws Exception 
    {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        Vector nameList = new Vector();
        Vector telList  = new Vector();
        while (true)
        {
            System.out.println("0.結束\n1.新增\n2.列印\n\n");
            System.out.print("請選擇功能 (0,1,2):");
            String select = in.readLine();
            if (select.equals("0"))
                return;
            if (select.equals("1"))
            {
                System.out.print("姓名:");
                String name = in.readLine();
                System.out.print("電話:");
                String tel  = in.readLine();
                nameList.add(name);
                telList.add(tel);
            }
            if (select.equals("2"))
            {
                System.out.println("=姓名=\t=電話=");
                for (int i=0; i<nameList.size(); i++)
                    System.out.println(nameList.get(i)+"\t"+telList.get(i));
            }
            System.out.println("\n\n");
        }
    }
}

矩陣：有轉置功能

class Matrix {
  public static void main(String[] args) {
    double A[][] = {{1,2}, {3,4}};
    double B[][] = {{5,6}, {7,8}};
    double C[][] = new double[2][2];
    double D[][] = new double[2][2];
    System.out.println("========A========");
    print(A);
    System.out.println("========B========");
    print(B);
    add(A, B, C);
    System.out.println("========C=A+B====");
    print(C);
    dot(A, B, D);
    System.out.println("========D=A*B====");
    print(D);
    System.out.println("========sum======");
    double sum = sum(D);
    System.out.println("sum(D)="+sum);
    not(D);
    System.out.println("========not(D)========");
    print(D);
 
    double X[][] = {{1,2,3}, {4, 5, 6}};
 
    System.out.println("==========X===========");
    print(X);
    double T[][] = transform(X);
    System.out.println("==========T===========");
    print(T);
 
  }
 
  public static void print(double A[][]) 
  {
    for (int i=0; i<A.length; i++) 
    {
      for (int j=0; j<A[0].length; j++) 
         System.out.print(A[i][j]+" ");
      System.out.println();
    }
  }
 
  public static void not(double A[][]) 
  {
    for (int i=0; i<A.length; i++) 
      for (int j=0; j<A[0].length; j++) 
        A[i][j] = -A[i][j];
  }
 
  public static double sum(double A[][]) 
  {
    double total = 0;
    for (int i=0; i<A.length; i++) 
      for (int j=0; j<A[0].length; j++) 
        total += A[i][j];
    return total;
  }
 
  public static void add(double A[][], double B[][], double C[][]) 
  {
    for (int i=0; i<A.length; i++) 
      for (int j=0; j<A[0].length; j++) 
        C[i][j] = A[i][j] + B[i][j];
  }
 
  public static void dot(double A[][], double B[][], double C[][]) 
  {
    for (int i=0; i<C.length; i++) 
      for (int j=0; j<C[0].length; j++) 
      {
        double sum = 0;
        for (int k=0; k<2; k++) 
            sum = sum+A[i][k]*B[k][j];
        C[i][j] = sum;
      }
  }
 
  public static double[][] transform(double A[][]) 
  {
    double T[][] = new double[A[0].length][A.length];
    for (int i=0; i<T.length; i++) 
      for (int j=0; j<T[0].length; j++) 
        T[i][j] = A[j][i];
    return T;
  }  
}

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page revision: 9, last edited: 06 Oct 2011 01:38
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