1. Array overview: An array is a container that stores multiple variables (elements). The data types of these multiple variables are the same.
2. Array concept:
Arrays store the same type of data. Data type A container with multiple elements
Arrays can store both basic data types and reference data types
3. Array definition format:
Format 1: Data type [] Array name (commonly used)
Format 2: Data type array name []
4. Array initialization:
Arrays in Java must Initialize first before use
The so-called initialization is to allocate memory space for the elements in the array and assign a value to each array element.
One kind of initialization, the initialization only specifies the length of the group, and the array is assigned an initial value by washing
The second type of initialization, the initial value of each element is specified during initialization, and the array length is determined by the system
Format: data type [] array name = new data type [array length];
The array length is actually the number of elements in the array Number.
Explanation: A value of type int is defined, and 3 ints can be stored in this array Type of value.
Memory allocation in JAVA
Stack; storage of local variables
Local variables are variables defined in methods or statements
Local variables are recycled immediately after use
2. Heap: stores new things
Every object has a first address value, which is a hexadecimal address
The data in each object has a default value
After use, it will be recycled by the garbage collector.
3. Method area
4. Common problems with array operations:
-Array index out-of-bounds exception, accessing an index value that does not exist in the array, such as int [ ] arr = new int[2]
This array exists arr[0] arr[1] arr[2]
If you output arr[3], it is an array out of bounds.
Null pointer exception, the array reference does not point to the object, but is operating on the elements in the object.
Exercise: Known array int[] arr= {11,22,33,44,55}
Traverse each element in the array.
public class Test05 {
<code>public static void main(String[] args) { <br>int[] arr = { 11, 22, 33, 44, 55 }; <br>for (int x = 0; x < 5; x++) { System.out.println(arr[x]); } }</code>
}
2 .Get the maximum value in the array
Principle of getting the maximum value of the array:
First use the first element in the array as a reference
Then get all the following elements and compare them with the reference object
If any element is larger than the reference object, leave it
After all comparisons, the largest element remains.
<code>public static void main(String[] args) { <br>int[] arr = { 11, 22, 33, 44, 55 }; <br>int max = arr[0]; <br>for (int x = 0; x < arr.length; x++) { <br>if (max < arr[x]) { <br>max = arr[x]; } } System.out.println(max); }</code>
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