Big Data Java Foundation fourth day job

Tag:java    bitwise operator    java heap size    

First question: Class bindemo{    public static void main (String[] args) {         //left: The first sign bit   must be moved off, so there is no (have | no) sign bit move one said.         byte plus_left = 9;         byte minus_left = -9;         System.out.println (plus_left << 2);//0000 1001 => 0010 0100 =  36        system.out.println (minus_left << 2);// 11111 0111  Mobile complement  => 1101 1100  complement  => 1010 0100 original code  =  -36        //sign right Shift: Positive 0, negative 1, sign bit normal movement.         byte plus_right = 9;         byte minus_right = -9;   &nbsP;    system.out.println (plus_right >> 2);//0000 1001 =>  0000 0010 = 2        system.out.println (Minus_ RIGHT&NBSP;&GT;&GT;&NBSP;2);//1111 0111  Mobile complement  => 1111 1101  complement  =>  1000 0011 Original code  = -3         //unsigned Right Shift: positive 0, negative 1, sign bit does not move.         byte unsigned_plus_right = 9;         byte unsigned_minus_right = -9;         system.out.println (unsigned_plus_right >>> 2);//0000 1001 =>  0000 0010 = 2        system.out.println ((Byte) ( UNSIGNED_MINUS_RIGHT&NBSP;&GT;&GT;&GT;&NBSP;2));//1111 0111  Mobile complement  => 1111 1101   Complement  => 1000 0011 Original Code  = -3                  byte unsigned_minus_right2 = -5;         system.out.println ((Byte) (unsigned_minus_right2 >>> 2));//1111 1011  Mobile complement  =>1111 1110  complement  => 1000 0010 original code  = -2    } } second question: Class bindemo{    public static void main (String[] args) {         string hex_value = changehex (one);         system.out.println (Hex_value);    }     public static string changehex (INT&NBSP;V) {         int lower = v & 0x0f;        int  upper =  (v &GT;&GT;&NBSP;4)  & 0x0f;         char[] arr  = {' 0 ', ' 1 ', ' 2 ', ' 3 ', ' 4 ', ' 5 ', ' 6 ', ' 7 ', ' 8 ', ' 9 ', ' A ', ' B ', ' C ', ' D ', ' E '};         return   "0x"  + arr[upper] + arr[lower];     }} Third question: Class bindemo{    public static void main (String[]  args) {        int sum_value = getsum (new int[]{ 1,5,7,9});         system.out.println (Sum_value);     }    public static int getsum (Int[] arr) {         int length = arr.length;         int total = 0;        for (int i=0;i <length;i++) {            total += arr[i];         }        return total;    }} Question Fourth:import java.util.arrays;class bindemo{    public static void  Main (String[] args) {        int[] copy_value =  Copyarr (new int[]{1,5,7,9});         system.out.println ( Arrays.tostring (Copy_value));     }    public static int[]  copyarr (Int[] arr) {        int length =  arr.length;        int[] new_arr = new int[ Arr.length];        for (int i=0;i<length;i++) {             new_arr[i] = arr[i];        }         return new_arr;    }} The fifth question:class bindemo{     public static void main (String[] args) {         while (True) {             System.out.println ("execute");         }    }} First step: Write a dead loop to perform the second step: JPS gets the PID of the execution third step:jmap -heap 14396  view the process information executed. heap configuration:   minheapfreeratio          = 0   MaxHeapFreeRatio         =  100   maxheapsize               = 2122317824  (2024.0MB)    newsize                  =  44564480  (42.5MB)    MaxNewSize                = 707264512  (674.5MB)    OldSize                   = 89653248  ( 85.5MB)    NewRatio                  = 2   SurvivorRatio             = 8   MetaspaceSize             = 21807104  (20.796875MB)     compressedclassspacesize = 1073741824  (1024.0MB)    MaxMetaspaceSize          = 17592186044415 mb   g1heapregionsize         =  0  (0.0MB) Fourth step: Java -xms<size>: Sets the initial Java heap size.         java -xmx<size>: Sets the maximum Java heap size.

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Big Data Java Foundation fourth day job