Java中的集合 replaceAll() 方法和示例

Java.util.Collections类的replaceAll()方法用于将列表中一个指定值的所有出现替换为另一个。更正式地，用 newVal 替换列表中的每个元素 e，使得

oldVal == null ? e==null : oldVal.equals(e) 

Note: This method has no effect on the size of the list.

参数：此方法将以下参数作为参数

• list：要进行替换的列表。
• oldVal：要替换的旧值。
• newVal：要替换 oldVal 的新值。

返回值：如果列表包含一个或多个元素 e，则此方法返回true ，如下所示，否则返回 false

oldVal== null ? e==null : oldVal.equals(e)

句法：

public static  boolean replaceAll(List list, T oldVal, T newVal)

示例 1：

Java

// Java program to demonstrate
// replaceAll() method for String value
 
// Importing utility classes
import java.util.*;
 
// Main class
public class GFG {
 
    // Main driver method
    public static void main(String[] argv) throws Exception
    {
 
        // Try block to check for exceptions
        try {
 
            // Creating a vector object of string type
            List vector = new Vector();
 
            // Populating the above Vector object
            // Custom input elements
            vector.add("A");
            vector.add("B");
            vector.add("A");
            vector.add("C");
 
            // Printing the vector
            System.out.println("Initial Vector :" + vector);
 
            // Replacing value
            // using replaceAll() method
            Collections.replaceAll(vector, "A", "TAJMAHAL");
 
            // Printing elements of Vector object after
            // replacing
            System.out.println("Vector after replace :"
                               + vector);
        }
 
        // Catch block to handle the exceptions
        catch (IllegalArgumentException e) {
 
            // Display message when exception occurs
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出

Initial Vector :[A, B, A, C]
Vector after replace :[TAJMAHAL, B, TAJMAHAL, C]

示例 2：

Java

// Java program to demonstrate
// replaceAll() method for Integer value
 
// importing utility classes
import java.util.*;
 
// Main class
public class GFG {
 
    // Main driver method
    public static void main(String[] argv) throws Exception
    {
 
        // Try block to check for exceptions
        try {
 
            // Creating object of List
            List vector = new Vector();
 
            // Populate the vector
            vector.add(20);
            vector.add(30);
            vector.add(20);
            vector.add(30);
 
            // Printing the vector before replacing
            // elements
            System.out.println("Initial values are :"
                               + vector);
 
            // Replacing value
            // using replaceAll() method
            Collections.replaceAll(vector, 20, 400);
 
            // Printing the vector after replacing elements
            System.out.println("Value after replace :"
                               + vector);
        }
 
        // Catch block to handle IllegalArgumentException
        catch (IllegalArgumentException e) {
 
            // Display the exceptions on the console
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出：

Initial values are :[20, 30, 20, 30]
Value after replace :[400, 30, 400, 30]