単純な関数リロード,intなどの数値範囲
2823 ワード
public class OverloadDemo {
static void f(float d) {
System.out.println("the argument is float");
} static void f(double d) {
System.out.println("the argument is double");
}
static void f(float d, double s) {
System.out.println("the argument is float and double");
}
static void f(double d, float s) {
System.out.println("the argument is double and float");
}
public static void main(String[] args) {
OverloadDemo.f(2); // , ,
// OverloadDemo.f(2, 3); ,
}
}
実行結果:the argument is float float float型変数はdoubleに付与できるが、逆に成立しないため、赤い部分の関数を呼び出す
2,int,byte,double,floatの最大値と最小値を計算する
import java.util.StringTokenizer;
public class MaxVaules {
private static final byte MAX_BYTE = Byte.MAX_VALUE;
private static final byte MIN_BYTE = Byte.MIN_VALUE;
private static final int MAX_INT = Integer.MAX_VALUE;
private static final int MIN_INT = Integer.MIN_VALUE;
private static final double MAX_DOUBLE = Double.MAX_VALUE;
private static final double MIN_DOUBLE = Double.MIN_VALUE;
private static final float MAX_FLOAT = Float.MAX_VALUE;
private static final float MIN_FLOAT = Float.MIN_VALUE;
public static void main(String[] args) {
System.out.println(MaxVaules.MAX_BYTE); // 127
System.out.println(MaxVaules.MIN_BYTE);// -128
System.out.println(MaxVaules.MAX_INT); //
System.out.println(MaxVaules.MIN_INT);
System.out.println(MaxVaules.MAX_FLOAT); // 3.4*10^38
System.out.println(MaxVaules.MAX_FLOAT);
System.out.println(MaxVaules.MAX_DOUBLE);// 1.79*10^308
System.out.println(MaxVaules.MIN_DOUBLE);
String a = new String("hello");
String b = "hello";
System.out.println(a == b); // false
float f = 4.2f;
Float ff = new Float(4.2);
System.out.println(f == ff); // true,
int x = 19;
int y = x << 1; // 2,
System.out.println(y);
y = x >> 1; // 2
System.out.println(y);
// String,StringBuffer,StringTokenizer
String story = "A long time ago";
StringTokenizer st = new StringTokenizer(story); // , ,
while (st.hasMoreElements())
System.out.println(st.nextToken());
}
}
結果は次のとおりです.
127
-128
2147483647
-2147483648
3.4028235E38
3.4028235E38
1.7976931348623157E308
4.9E-324
false
true
38
9
A
long
time
ago