20110609 Java 練習小記

public class Sample1 {
//練習取得字串的長度與文字 
public static void main(String[] args) {
  String str = "Hello";

  //取得字串的第一個字, 索引值一樣從0開始  
  char char1 = str.charAt(0);
  char char2 = str.charAt(1);

  //傳回字串的長度  
   int len = str.length();

  System.out.println(str+"第1個字是"+char1);
  System.out.println(str+"第2個字是"+char2);
  System.out.println(str+"的長度是"+len);
 }
}

import java.io.*;
public class Sample2 {
//轉換大小寫 
public static void main(String[] args) throws IOException
 {
  System.out.println("請輸入英文字");
  BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  String str = br.readLine();

  //轉成大寫  
   String stru = str.toUpperCase();
  //轉成小寫  
   String strl = str.toLowerCase();

  System.out.println("轉成大寫"+stru);
  System.out.println("轉成小寫"+strl);
 }
}

import java.io.*;
public class Sample3 {
//搜尋文字練習 
  public static void main(String[] args) throws IOException
 {
  System.out.println("請輸入字串");

  BufferedReader br = new BufferedReader( new InputStreamReader(System.in));
  String str1 = br.readLine();

  System.out.println("請輸入要檢索的文字");

  String str2 = br.readLine();

  //取出輸入的第一個字  
   char ch = str2.charAt(0);
  //indexOf 會傳回是字串的第幾個字, 一樣從0開始算  //如果找不到就會傳回 -1  
  int num = str1.indexOf(ch);
  System.out.println("num="+num);

  if ( num != -1 )
  {
   System.out.println(str1+"的第"+(num+1)+"個字["+ch+"]已經找到了");
  }
  else
  {
   System.out.println(str1+"中沒有["+ch+"]這個字");
  }
 }
}

import java.io.*;
public class Sample4 {
 public static void main(String[] args) throws IOException
 {
  System.out.println("請輸入字串");
  BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  String str1 = br.readLine();

  System.out.println("請輸入要增加的字串");
  String str2 = br.readLine();

  //使用 StringBuffer 處理字串  
   StringBuffer sb = new StringBuffer(str1);
  //附加 str2  
   sb.append(str2);

  System.out.println(str1+"後增加"+str2+"就等於"+sb);
 }
}

import java.io.*;
public class Sample5 {
 public static void main(String[] args) throws IOException
 {
  System.out.println("請輸入2個整數");

  BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

  String str1 = br.readLine();
  String str2 = br.readLine();

  //轉成 integer  
  int num1 = Integer.parseInt(str1);
  int num2 = Integer.parseInt(str2);

  int ans = Math.max(num1, num2);

  System.out.println(num1+"與"+num2+"兩個其中較大的是"+ans);
 }
}

package chapter10.lab6;
//練習 類別型態變數
class Car
{
 private int num;
 private double gas;

 //建構元 
 public Car()
 {
  num = 0;
  gas = 0.0;
  System.out.println("初始化汽車");
 }

 public void setCar(int n, double g)
 {
  num = n;
  gas = g;
  System.out.println("設定車號為"+num+"\t改變油量為"+gas);
 }

 public void show()
 {
  System.out.println("車號為"+num+"\t油量為"+gas);
 }

}
public class Sample6 {
 public static void main(String[] args) {
  //宣告 car1  
  Car car1;
  System.out.println("宣告car1");
  //產生一個新的物件, 並指定給 car1  

   car1 = new Car();
  //設定初始值  
   car1.setCar(1234, 20.5);

  Car car2;
  System.out.println("宣告 car2");

  //兩個類別變數 car1 與 car2 指到同一個汽車物件  
  car2 = car1;
  System.out.println("將car1 指定到 car2");

  System.out.println("car1 所指的");
  car1.show();

  System.out.println("car2 所指的");
  car2.show();
 }
}

package chapter10.lab7;
class Car
{
 private int num;
 private double gas;

 public Car()
 {
  num = 0;
  gas = 0;
  System.out.println("初始化汽車");
 }

 public void setCar(int n, double g)
 {
  num = n;
  gas = g;
  System.out.println("設定車號為"+num+"\t設定油量為"+gas);
 }

 public void show()
 {
  System.out.println("車號為"+num+"\n油量為"+gas);
 }


}
public class Sample7 {
 public static void main(String[] args) {
  Car car1;
  System.out.println("宣告 car1");

  car1 = new Car();
  car1.setCar(1234, 20.5);

  Car car2;
  System.out.println("宣告 car2");

  car2 = car1;
  System.out.println("將 car1 指定給 car2");

  System.out.println("car1 所指的");
  car1.show();
  System.out.println("car2所指的");
  car2.show();
  //藉由變更物件的內容, 來驗證兩個變數指到同一個物件  
  System.out.println("改變car1 的內容");
  car1.setCar(2345, 30.5);

  System.out.println("car1 所指的");
  car1.show();
  System.out.println("car2所指的");
  car2.show();

 }
}

package chapter10.lab8;//使用類別變數作為引數
class Car
{
 private int num;
 private double gas;
 //使用類別型態變數 
 private String name;

 public Car()
 {
  num = 0;
  gas = 0;
  name = "沒有名稱";
  System.out.println("初始化汽車");
 }

 public void secCar(int n, double g)
 {
  num = n;
  gas = g;
  System.out.println("設定車號"+num+"設定油量為"+gas);
 }

 public void setName(String nm)
 {
  name = nm;
  System.out.println("設定名稱為"+name);
 }

 public void show()
 {
  System.out.println("車號是"+num);
  System.out.println("汽油量為"+gas);
  System.out.println("名稱為"+name);
 }
}
public class Sample8 {
 public static void main(String[] args) {
  Car car1;
  car1 = new Car();

  car1.show();

  int number = 1234;
  double gasoline = 20.5;
  String str = "1號車";

  car1.secCar(number, gasoline);
  car1.setName(str);

  car1.show();
 }
}