用示例替换 Java 中的 Collections replaceAll()方法
原文:https://www . geesforgeks . org/collections-replace all-method-in-Java-with-examples/
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。更正式地说,用 newVal 替换列表中的每个元素 e,这样
oldVal == null ? e==null : oldVal.equals(e)
注意:此方法对列表大小没有影响。
参数:该方法将以下参数作为参数
- 列表:要进行替换的列表。
- 旧值:要替换的旧值。
- 新值:替换旧值的新值。
返回值:如果列表包含如下所示的一个或多个元素 e,则该方法返回 true 否则返回 false
oldVal== null ? e==null : oldVal.equals(e)
语法:
public static boolean replaceAll(List list, T oldVal, T newVal)
例 1:
Java 语言(一种计算机语言,尤用于创建网站)
// 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<String> vector = new Vector<String>();
// 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");
// Printitng 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);
}
}
}
Output
Initial Vector :[A, B, A, C]
Vector after replace :[TAJMAHAL, B, TAJMAHAL, C]
例 2:
Java 语言(一种计算机语言,尤用于创建网站)
// 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<String>
List<Integer> vector = new Vector<Integer>();
// Populate the vector
vector.add(20);
vector.add(30);
vector.add(20);
vector.add(30);
// Printing the vector before replacing
// elemements
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);
}
}
}
Output:
Initial values are :[20, 30, 20, 30]
Value after replace :[400, 30, 400, 30]
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