Leak Check (Java)

First, an anonymous array:

Java provides a simplified form of writing that creates an array object and gives the initial value at the same time
Int[] A = {1,2,5,4};
Reinitialize an array without creating a new variable

int b[] = {1,2,3,4};
A = b;
Simplified: a = new int[]{1,2,3,4};

See the code:

public class Main{public static void Main (string[] args) {///anonymous array defined by new int[]{1,5,1,9} int a[] = {1,5,1,9};int b[];b = A; System.out.println (b[1]); b = New int[]{1,5,1,9};//This is a simplified System.out.println (b[1]) of the above three lines of code;}}

Second, array copy:

int ary[] = {1,2,3,4,5,6,7,8,9,10};

Copies all elements of an array ary to array b

int b[] = arrays.copyof (ary,ary.length);

Changing the size of an array ary

ary = arrays.copyof (ary,2*ary.length);

Import Java.lang.reflect.array;import java.lang.reflect.constructor;import java.sql.date;import java.util.Arrays; public class Main{public static void Main (string[] args) {int ary[] = {1,2,3,4,5,6,7,8,9,10};//SYSTEM.OUT.PRINTLN ( ary.length); int b[] = arrays.copyof (ary,ary.length);//Copy the elements of Ary to BSystem.out.println (b[1]); System.out.println (b.length);//b the same number of elements and ary array ary = arrays.copyof (ary, 2*ary.length);// The size of the ARY array is larger by twice Times System.out.println (Ary.length);}}

three, array sorting:

Quickly sort the values of an element in a array

Arrays.sort (a);

Code:

Import Java.util.arrays;public class main{public static void Main (string[] args) {int ary[] = {8,4,56,6,7,21,1}; Arrays.sort (ary);//for (int i = 0;i< ary.length;i++) for (int i:ary) {//system.out.println ("ary[" +i+ "] =" +ary[i]); System.out.println ("ary[" +i+ "] =" +i);}}}

for (int i = 0;i<ary.length;i++) {System.out.println (Ary[i]),}↓for (int i:ary) System.out.println (i);//both equivalent

Four, the Java random number generation way:

Apply the random method in the math class

(int) (Math.random () *n) method randomly generates a random floating-point number between 0 and 1 (containing 0, not 1), which is multiplied by the float to get the random numbers between 0 and n-1.

Import Java.util.arrays;public class main{public static void Main (string[] args) {int ary[] = {8,4,56,6,7,21,1}; Arrays.sort (ary); int ran = (int) (Math.random () *ary.length); System.out.println ("Generated random number is" +ran); System.out.println ("Printed array element" +ary[ran]);}}

v. Relationships between classes and classes:

1. Dependency (use a)
2. Aggregation (has a)
3. Inheritance (is a)
1. Dependency: If a class's methods manipulate objects of another class, then we say that one class depends on another class

PS: You should minimize the number of interdependent classes as much as possible, and if Class A does not know the existence of Class B, it will not care about any changes in class B (b changes will not cause any bugs in class A)
Terminology: Minimizing the degree of coupling between classes


2. Aggregation: Class A object contains object of Class B


3. Inheritance


Date class, whose object describes a point in time

System.out.println (New Date ());//Anonymous Object

You can also apply a method to the object you just created, and the date class has a ToString method that returns a string description of the date

String s = new Date (). toString ();
In both cases, the constructed object is used only once, if you want to use date Bir = new Date () multiple times;

Six, there is an important difference between objects and objects:

Example: Date d;//defines an object variable D

String s = d.tostring ();

D is not an object, actually there is no reference object, it is just an object variable, a name, a code, you cannot apply the date method to this variable

Therefore, you must first initialize the variable d, here are two options:
1. Class with the new constructed object.

D = new Date ();

2. Let this variable refer to an existing object

Date dir = new Date ();

D = bir;//Now two variables share an object

Leak Check (Java)