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class Parent { | |
public void angry() { | |
System.out.println("こら"); | |
} | |
} | |
class Child extends Parent{ | |
public void sorry() { | |
System.out.println("ごめん"); | |
} |
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class Parent { | |
public void angry() { | |
System.out.println("こら"); | |
} | |
} | |
class Child extends Parent{ | |
public void sorry() { | |
System.out.println("ごめん"); | |
} |
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class Parent { | |
public void angry() { | |
System.out.println("こら"); | |
} | |
} | |
class Child extends Parent{ | |
public void sorry() { | |
System.out.println("ごめん"); | |
} |
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public static void main(String[] a) { // エントリーポイント | |
} | |
public static void Main(String[] args){ // MainはNG,mainであること | |
} | |
public static void main(int[] args){ // 単なるオーバーロードなのでコンパイルは通るがエントリーポイントではない | |
} |
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public class Main { | |
static int i; | |
static boolean flag; | |
static short s; | |
static float f; | |
static double d; | |
static long l; | |
static char c; | |
static byte b; | |
public static void main(String[] args) { |
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public class Main { | |
static char i = 65535; // これはOK | |
// static char j = 65536; // これはコンパイルエラーなのでコメントする | |
static int k = 100000; // int型 | |
public static void main(String[] args) { | |
int x = i; // char型からint型に暗黙変換できる | |
System.out.println(x); // 65535となる | |
System.out.println(k); // 100000となる | |
char xx = (char)k; // int型からchar型に変換する場合は明示的にキャストする | |
System.out.println(xx); // 蚠となる |
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public class Main { | |
static float f; | |
static double d; | |
public static void main(String[] args) { | |
f = 3.0f; // fかFが必須、省くとコンパイルエラー | |
d = 4.0; // dかDは必須ではない | |
} | |
} |
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public class Employee { | |
private int age; | |
private String name; | |
public Employee(int age, String name) { | |
this.age = age; | |
this.name = name; | |
} | |
public boolean equals(Object obj) { | |
if(obj == null) return false; // パラメータがnullの場合はfalseを返すのがequalsメソッドの条件 | |
return this.name == ((Employee)obj).name; // nameだけ同値ならtrueとしている |
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public class Main { | |
public static void main(String[] args) { | |
Employee emp1 = new Employee(10, "takahashi"); | |
Employee emp2 = new Employee(20, "takahashi"); | |
System.out.println(emp1.equals(emp2)); // nameだけで同値なのでtrueとなる | |
} | |
} |
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public class Main { | |
public static void main(String[] args) { | |
String str1 = "aa"; | |
String str2 = "aa"; // 使いまわすため同一インスタンスとなる | |
System.out.println(str1 == str2); // 同一のため、true | |
System.out.println(str1.equals(str2)); // 同値のため、true | |
} | |
} |