1. 判斷是否為奇數:
public static boolean isOdd(int i) { return i %2 != 0 ; }
#2. System. out.println(2.0 - 1.1); 輸出:0.89999999 99999999 (Double型的)
System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("1.new BigDecimal("2.00").subtract(new BigDecimal("1.10")); --輸出0.90 要加上引號,否則會有小數。
System.out.println(new BigDecimal("2.01").subtract(new BigDecimal("1.65"))); -- 輸出0.36
<code><code><code><code>
<code><code><code>##System.out.println(new BigDecimal(2.0).subtract(new BigDecimal(1.1))); -- 輸出 0.899 99999999 99999111 82158029 9874766#S747646215802962147626#. out.printf ("%.2f\n", 2.0-1.115); --輸出:0.89<code>
final long MICROS_PER_DAY = 24 * 60 * 60 * 1000 * 1000 ;final long MILLIS_PER_DAY = 24 * 60 * 60 * 1000;
System.out.println(24 * 60 * 60 * 1000 * 1000); 0654080 , 當做了int型,導致越界。System.out.println(24 * 60 * 60 * 1000 ); 中對 含AY/MILLIS_PER_DAY); --- 輸出:5
對於長整型的計算,要加上L: System.out.println(24L * 60 * 60 * 1000 * 1000); --- 輸出: 86400000 000
####
System.out.println("H" + "a"); 輸出: Ha
System.out.println('H' + 'a'); 169
#char[] numbers = {'1','2','3'};
System.out.println("a" + numbers); 輸出:a[C@c3c749
#Prints a String and then terminate the line. This method behaves as though it invokes
print(String) and then println(). System.out.println(numbers); 輸出:123void java.io.PrintStream.println(char[] x) 重載的方法
Prints an array of characters and then terminate the line. This method behaves as though it invokes <code>#print(char[])<code> and then println().<code> \u0022 是雙引號的unicode編碼。 <code>System.out.println("a\u0022 + \u0022b ".length()); 相當於: System.out.println("a" + "b ".length()); , 輸出a2 。 (b後面有一個空格) System.out.println(Test.class.getName().replace(".","/")) ; 輸出: com/Test
String java.lang.String.replace(CharSequence target, CharSequence replacement)
Replaces each substring of this string that matches the literal target sequence with the ified lite sequence. The replacement proceeds from the beginning of the string to the end, for example, replacing "aa" with "b" in the string "aaa" will result in "ba" rather than "ab".
Constructs a string buffer with no characters in it and the specified initial capacity.
Parameters:
capacity the initial capacity.
System.out.println(word); 輸出中交換
System.out.println(".append(輸出a
int j = 0;
for(int i = 0; i < 100; i++){
# j = j++;
System.out.println(j);
}
輸出100 行0 (j的值總是0):
0
0
……
final int END=Integer.MAX_VALUE; int //2147483647##END count = 0;
for(int i = START; i <= END; i++){
count++;
System.out.println(i); -- 死迴圈。 當 i 達到 2147483647 ,再增加會變成負數。
}
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