Practical combat of java's Arrays tool class

The java.util.Arrays class can conveniently operate arrays, and all methods it provides are static. Static methods belong to classes, not objects of classes. So you can directly use the class name plus the method name to call it. Arrays, as a tool class, can operate arrays very well. The following introduces several functions that are mainly used.

1.fill method

The fill method is mainly used to fill arrays. Here we take the simplest int type (the same as other types)

Look at the fill source code of Arrays

Example code:

Java code

publicstaticvoidmain(String[] args) {
inta[]=newint[5];
//fill填充数组
Arrays.fill(a,1);
for(inti=0;i<5;i++)//输出5个1
System.out.println(a[i]);
}

Fill part of the array source code:

Example:

Java code

publicstaticvoidmain(String[] args) {
inta[]=newint[5];
//fill填充数组
Arrays.fill(a,1,2,1);
for(inti=0;i<5;i++)//a[1]=1，其余默认为0
System.out.println(a[i]);
}

2.sort method

You can tell from the method name that it is used to sort the array. It still uses the int type, and the other types are the same.

Same as sorting the entire array, such as

Java code

publicstaticvoidmain(String[] args) {
inta[]={2,4,1,3,7};
Arrays.sort(a);
for(inti=0;i<5;i++)//升序
System.out.println(a[i]);
}

Specify partial sorting of the array:

Java code

publicstaticvoidmain(String[] args) {
inta[]={2,4,1,3,7};
Arrays.sort(a,1,4); //输出2,1,3,4,7
for(inti=0;i<5;i++)
System.out.println(a[i]);
}

3.equals method

is used to compare whether the element values ​​​​in two arrays are equal, or to look at the int type array. Look at the Arrays source code

Example:

Java code

publicstaticvoidmain(String[] args) {
inta[]={2,4,1,3,7};
inta1[]={2,4,1,5,7};
System.out.println(Arrays.equals(a1, a)); //输出false
}

4.binarySearch method

The binarySearch method can perform binary search operations on sorted arrays. See the source code as follows

Example:

Java code

publicstaticvoidmain(String[] args) {
inta[]={2,4,1,3,7};
Arrays.sort(a);//先排序
System.out.println(Arrays.binarySearch(a, 4));//二分查找，输出3
}

5.copyof method

Copy an array. The array returned by the copyOf() method of Arrays is a new array object, so if you change the element value in the returned array, it will not affect the original array.

For example:

Java code

importjava.util.Arrays;
publicclassArrayDemo {
publicstaticvoidmain(String[] args) {
int[] arr1 = {1, 2, 3, 4, 5};
int[] arr2 = Arrays.copyOf(arr1, arr1.length);
for(inti = 0; i < arr2.length; i++)
System.out.print(arr2[i] + " ");
System.out.println();
}
}

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