java常用类库之数组操作类

Arrays定义了很多与数组有关的基本操作

public static boolean equals (int[ ] a,int [ ] b)

public static void fill(int[] a,int val)

public static void sort(int[ ] a)

public static int binarySearch(int[ ] a,int key)

public static String toString (int[ ] a)

public class ArraysDemo {
	public static void main(String[] args) {
		int i1[] = { 1, 2, 3, 4, 5, 6 }; // 两个数组内容一样
		int i2[] = { 6, 5, 4, 3, 2, 1 }; // 两个数组内容一样
		Arrays.sort(i2);
		System.out.println(Arrays.equals(i1, i2));
		Arrays.fill(i2, 3); // 将数组2的内容全部填充为3
		System.out.println(Arrays.toString(i2));// 输出内容
	}

}

这里再说一下java中的比较器Comparable,通过实现这个接口并重写其中的compareTo方法可以实现对象之间的比较

class Student implements Comparable<Student> { // 实现比较器，并指定泛型
	private int stuno;
	private String name;
	private int age;
	private float score;

	public Student(int stuno, String name, int age, float score) {
		this.stuno = stuno;
		this.name = name;
		this.age = age;
		this.score = score;
	}

	public int compareTo(Student stu) {
		if (this.score > stu.score) {
			return -1;
		} else if (this.score < stu.score) {
			return 1;
		} else {
			if (this.age > stu.age) {
				return 1;
			} else if (this.age < stu.age) {
				return -1;
			} else {
				return 0;
			}
		}
	}

	public String toString() { // 覆写toString()
		return "学生编号：" + this.stuno + "；姓名：" + this.name + "；年龄：" + this.age
				+ "；成绩：" + this.score;
	}

}
public class CompareableDemo01 {
	public static void main(String[] args) {
		Student stu[] = { new Student(1, "张三", 21, 99.1f),
				new Student(2, "李四", 20, 99.1f),
				new Student(3, "王五", 21, 89.1f),
				new Student(4, "赵六", 21, 80.1f),
				new Student(5, "孙七", 19, 80.1f) };
		System.out.println("============== 数组声明之前 ===============");
		print(stu);
		System.out.println("============== 数组排序之后 ===============");
		Arrays.sort(stu);// 排序
		print(stu);
	}

	public static void print(Student stu[]) {
		for (int i = 0; i < stu.length; i++) {
			System.out.println(stu[i]);
		}
	}
}

对象的克隆、

通过实现cloneable可以使得类的实例化对象具有被克隆能力

class Person implements Cloneable {// 表示此类的对象可以被克隆
	private String name;

	public Person(String name) {
		this.name = name;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String toString() {
		return "姓名：" + this.getName();
	}

	public Object clone() throws CloneNotSupportedException {
		return super.clone();
	}

}

public class CloneDemo {

	public static void main(String[] args) throws CloneNotSupportedException {
		Person per1 = new Person("张三");
		Person per2 = (Person)per1.clone() ;		
		per2.setName("李四") ;
		System.out.println(per1) ;
		System.out.println(per2) ;
	}

}

此时两个对象堆内存空间互不影响。